Vacuum signal

[jrvariel48]

On a blown motor, where should I get the vacuum signal for the distributor? I keep hearing conflicting reports of getting it from the carb as oppssed to the intake, but I would like to hear from the Flathead guys!
Thanks,
Joe

[JSeery]

I've never ran a blower, but if you connect the vacuum line to a pressurized intake you are not going to get a vacuum.

[flatheadmurre]

When the carb is closed the blower isn´t getting air so you get nothing to push in....
So vacuum connection at manifold.
Hooking it up to the carb you can get vacuum advance at WOT.

[Kruzn40]

...

[flatheadmurre]

If you take the vacuumsignal between blower and carb you can get vacuum advance at WOT...
Vacuum should be taken at manifold and reflect what happens there...no matter how you are feeding the engine.
If there was a positive pressure feed at all times you would have a runaway engine never idling...

[Kruzn40]

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...

[51 MERC-CT]

Originally Posted by flatheadmurre

When the carb is closed the blower isn´t getting air so you get nothing to push in....
So vacuum connection at manifold.
Hooking it up to the carb you can get vacuum advance at VOT.

Originally Posted by flatheadmurre

If you take the vacuumsignal between blower and carb you can get vacuum advance at VOT...
Vacuum should be taken at manifold and reflect what happens there...no matter how you are feeding the engine.
If there was a positive pressure feed at all times you would have a runaway engine never idling...

For me and some of the rest of us who don't understand what may or may not be 'tweet-speak', what is VOT?

[Karl]

Ja vhat is VOT?

[flatheadmurre]

Sorry...should have been WOT(wide open throttle).
I apologize for being lazy not writing it in full and on top of that louzy at spelling...

[Frank Miller]

First things first. What kind of distributor are you running? The next thing is has it been set up for this blower? I do not know enough to answer the questions but I do know that running a blower may require a different advance curve than a stock motor. Also what kind of carb are you running and are there any modifications to it?

[flatheadmurre]

Going for boostretard with a conventional distributor takes totally different setup.
Depends on how much boost you have and if detonation/knocking will be an issue.
On a street flathead with a mild boost you should get away without it...or hide an electronic module taking care of the advance for you.

[BUBBAS IGNITION]

Wow , wide range of answers.
The answer depends on what distributor are you trying to run...?????? A picture would help.

Best advise is forget vacuum advance on a blown engine, tune the ignition to run with the blower boost etc and drive it !!!!!!! A blown spark advance would differ a lot from a non blower engine....................

[jrvariel48]

Sorry, It's a Chevy set up by a Barner. It was set up for a blower. Advance is 24 degrees at 2800 rpm.

[JSeery]

There is an interesting thread on the HAMB on this topic.

https://www.jalopyjournal.com/forum/...vacuum.412468/

I'm with Bubba, I have run full mechanical advance on several engines with very good success.

[jrvariel48]

Originally Posted by JSeery

There is an interesting thread on the HAMB on this topic.

https://www.jalopyjournal.com/forum/...vacuum.412468/

I'm with Bubba, I have run full mechanical advance on several engines with very good success.

Can you post a link please?

[JSeery]

Originally Posted by jrvariel48

Can you post a link please?

I did

[jrvariel48]

Originally Posted by JSeery

I did

Sorry! Got it! Read the whole thing & now I'm totally confused!!!

[JSeery]

Originally Posted by jrvariel48

Sorry! Got it! Read the whole thing & now I'm totally confused!!!

That was sort of my conclusion as well. As I aready stated I have run a lot of mechanical only ignitions and was very satisfied with the results.

[Fordors]

I run an off topic blown engine and have vacuum advance on it connected to the manifold. My combination has a relatively mild cam, a 6-71 @ 15% under with two 600 Holleys running direct linkage. Boost is 6 pounds maximum but that is when you open the carbs, when cruising down the road it always is in vacuum and for that reason I decided to run vacuum advance. Connected to the manifold it will only provide the extra advance when you need it, if you give it enough throttle to go into boost the vacuum canister will immediately retard your timing to the maximum of your mechanical advance.
I guess it all depends how you intend to drive, will it be a highway car or just a local cruiser? Any car should be a total, thought out combination for what you want out of it.

[jrvariel48]

Fordors I use the car for around town and some highway runs. It's a stock 59L motor.
Thanks

[Frank Miller]

To answer your question, the chevy distributor hooks to manifold vacuum.

[Ronnieroadster]

Since you have a stock 59A with a blower I would gather its not going to be a high boost producing combination. To get a good vacuum signal go between the carb and the top of the blower this way the signal will be consistant for what you need.
The advance setting in your converted chevy dizzy is a bit high coming in at 2800 if I read that correctly. It would be better to have full advance at a lower point more like 2400.
Ronnieroadster

[Fordors]

If you source your vacuum above the blower you will have your mechanical plus the 16° of vacuum advance the canister might provide available at all times. For example if you open the throttle and go into boost you will have your 24° of mechanical and 16° vacuum, and I don't think your pistons will be happy with 40° at boost.
When cruising along the air/fuel mixture is leaner than at full throttle and that lean mixture will take longer to burn and that is where you need the vacuum advance. Open the carb and richen the mixture and you would have too much advance with the vacuum taken above the blower. With the vacuum taken below the blower you will not be getting vacuum advance when the throttle is opened.
Admittedly I'm not a flathead guy so I don't know what vacuum your engine is expected to idle at but keep in mind there are different vacuum canisters available. A canister bracket stamped B1 will provide 0° @ 8" and 16° @ 16", the B20 will give 0° @ 6" and 16° @ 12" and the B28 gives 0° @ 4" and 16° @ 8". As the numbers show the drop in vacuum reduces the amount of advance. NAPA stores can get any of these for you.

[Ronnieroadster]

Originally Posted by Fordors

If you source your vacuum above the blower you will have your mechanical plus the 16° of vacuum advance the canister might provide available at all times. For example if you open the throttle and go into boost you will have your 24° of mechanical and 16° vacuum, and I don't think your pistons will be happy with 40° at boost.
When cruising along the air/fuel mixture is leaner than at full throttle and that lean mixture will take longer to burn and that is where you need the vacuum advance. Open the carb and richen the mixture and you would have too much advance with the vacuum taken above the blower. With the vacuum taken below the blower you will not be getting vacuum advance when the throttle is opened.
Admittedly I'm not a flathead guy so I don't know what vacuum your engine is expected to idle at but keep in mind there are different vacuum canisters available. A canister bracket stamped B1 will provide 0° @ 8" and 16° @ 16", the B20 will give 0° @ 6" and 16° @ 12" and the B28 gives 0° @ 4" and 16° @ 8". As the numbers show the drop in vacuum reduces the amount of advance. NAPA stores can get any of these for you.

WOW I had no idea I was doing it all wrong for so long taking the signal from below the carb and above the blower! But then again Im a flathead guy who knows how to do it and has proven sucess JUST SAYING
Thought the total advance he has is a max of 24 seems someones math is off.

[Charlie ny]

Hi Joe,
I just now got back into town, I rec'd your email and I'll answer your question here. I'm with Ronnie, below the carb and above the blower ,that's where the vac is that the can understands. Don't sweat the can for now get carb dialed in, an A?F meter is priceless for this. The distributor will be close but none the less get the wax out of your ears and listen for any detonation. This is hot rodding, take a step at a time.
Charlie ny

[Fordors]

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In my experience I have seen constant vacuum above the blower and below the carbs. When the vacuum does not drop off how do you limit the vacuum advance when the engine is in boost? If the mechanical advance is 24* and you have 16* vacuum advance that still equals 40* in my book.
In the case of Holley carbs why is it that they are boost referenced to see the low vacuum that opens the power valves when the vacuum drops?

[Frank Miller]

He has 26 total. If the vacuum is 10 of that then then 14 is mechanical. When you stomp on the gas then the vacuum drops off giving a slight retard and avoiding detonation. Back to cruise and you get the full 26. I believe that is how Charlie explained it to me once.

[jrvariel48]

There's a spacer in between the carb and the blower that has a port in it. Is that where I should get the vacuum from?

[Ronnieroadster]

Originally Posted by jrvariel48

There's a spacer in between the carb and the blower that has a port in it. Is that where I should get the vacuum from?

Yes thats a perfect location to pick up the vacuum signal.

[jrvariel48]

Originally Posted by Ronnieroadster

Yes thats a perfect location to pick up the vacuum signal.

Thank you Ronnie!

[Bored&Stroked]

Well - might as well stick my big fat nose into this . . . and see how many folks will punch it! LOL

Truth be told, nobody can tell you how much advance your combination needs - given that I'll bet none of us have ever ran it and I sure as heck don't know your 'boost curve' and how it relates to your timing curve . . . let alone how much fuel your engine needs under what conditions.

So - here are a couple things from my experience with blown flatheads, blown OHVs and turbo OHVs:

1) On a street engine, running pump gas, you usually want to take timing back out under boost (if you have that option). A good rule of thumb is about 1 degree of timing for every pound of boost (good place to start).

Or - just don't run so much timing.

2) Your distributor is NOT setup for a flathead - as it has 12 degrees of advance in it (24 crank) - which is standard Chevy. I setup my distributors/mags with about 8 degrees of advance (16 crank) - and the rest comes from initial timing.

3) Total Degrees of Advance - Under Boost: I would start with 18 degrees, then slowly inch up and watch for detonation on the plugs. On a street flathead, if you are making any boost, it is doubtful that you'll be able to run more than about 20 - 22 total degrees under load and boost. Or - you'll detonate it. (On a SCoT blown 286 cube motor, I used to run a locked-down Harman Collins mag - at 18 degrees of timing. My max boost was about 7 - 8 lbs).

4) Vacuum Advance Canister: They are hard to run with a blower, unless you spend some time to figure out exactly how much advance you're getting - under what conditions. I used to run a special advance/retard vacuum can on my turbo motors (20+ years ago). The vacuum port was plumbed under the carb and the boost port was plumbed under the blower (manifold pressure). As the boost came up, it forced the can to retard the timing. I don't think you can buy such a beast any more.

5) So - What to Do: The answer is - figure it out!. I would have a vacuum gauge under the carb, a boost gauge in the manifold, a tach and an AFR gauge. Before you begin, you need to know how many degrees of advance the vacuum can will add in - at what vacuum. This can be tested on a good ole' Sun distributor machine (with a vacuum setup). It is very important to have a curve of vacuum - versus advance . . . so you know exactly what you'll have under which vacuum condition).

Then, you drive the car and monitor the gauges. If it continues to have high vacuum while the boost is coming up . . . then you know how much total advance you're going to be running . . . and it better not be more than what I talked about up above.

Now when you're not on the throttle (under boost), the vacuum advance can be higher and it will help fuel mileage.

6) Or - Plan B: If you don't have the above setup (gauges, meters, sensors, etc), then you might consider running just mechanical advance and initial timing. This is probably the safest method . . . unless you go another route to a computerized timing control with boost retard (MSD) - where you can tune the advance curve to do exactly what you need - given your boost/load conditions.

So there yah have it . . . now wasn't that easy! LOL

D

[flatheadmurre]

I still think vacuum should be taken out of the manifold where it reflects what going into the engine.
Taking it under the carb may or may not work...if you have a moderate flowing carb you may get vacuum advance at times you don´t want that way.
As others said it´s not a bolt on aplication you will have to fine tune it to fit your setup.
Now go bolt it on and enjoy your ride

[JSeery]

Related to what B&S posted, I have helped my son set up turbo setups. It takes a lot of gauges, a lot of data recording and a lot of trial runs! And we had the benefit of computer programs!!

[jrvariel48]

Man, that sounds discouraging! Lol! I'm going to do my best with the help of all you Barners. Please don't grow weary of all the questions to come! I will need all the help I can get.
Thank Joe

[Ronnieroadster]

Originally Posted by jrvariel48

Man, that sounds discouraging! Lol! I'm going to do my best with the help of all you Barners. Please don't grow weary of all the questions to come! I will need all the help I can get.
Thank Joe

Joe don't try to over think what you need to do. When you set the initial timing on your engine say its 10 to 12 degrees you add that number to the advance in the distributor so the total combined is no more than 24 degrees. If you keep that in mind you will be fine with you combination its a simple matter no extreme ideas or theory's are needed.
Ronnieroadster

[jrvariel48]

Originally Posted by Ronnieroadster

Joe don't try to over think what you need to do. When you set the initial timing on your engine say its 10 to 12 degrees you add that number to the advance in the distributor so the total combined is no more than 24 degrees. If you keep that in mind you will be fine with you combination its a simple matter no extreme ideas or theory's are needed.
Ronnieroadster

Thanks Ronnie!

[Bored&Stroked]

Ronnie is exactly right - it is the total that matters (as well as when it comes in).

Notice the 24 total degrees in his post . . . this is the reason why having a SBC mechanical advance curve of 24 degrees in the distributor - PLUS additional vacuum advance is a problem. Send your distributor to Bubba or Charlie and have them change the mechanical advance curve to better fit a flathead - that will be a good start. Just ensure that you don't throw too much advance at it (especially under boost), then tune from there . . .

Best of luck . . .
B&S

[jrvariel48]

Originally Posted by Bored&Stroked

Ronnie is exactly right - it is the total that matters (as well as when it comes in).

Notice the 24 total degrees in his post . . . this is the reason why having a SBC mechanical advance curve of 24 degrees in the distributor - PLUS additional vacuum advance is a problem. Send your distributor to Bubba or Charlie and have them change the mechanical advance curve to better fit a flathead - that will be a good start. Just ensure that you don't throw too much advance at it (especially under boost), then tune from there . . .

Best of luck . . .
B&S

Thanks B&S, That's what I'm doing! Charlie will handle this one.
I also emailed Joe Abbin and here's what he said.

Joe Abbin
May 26 (4 days ago)

Hi Joe,
Good question, because you can do major engine damage if you do it wrong.
You don't hook up the vacuum advance at all. I recommend a boost retard device such as the MSD 6BTM, p/n 6462 with 24 degrees total, or reduce total timing to 18 degrees (4 degrees initial) without. You can read all about supercharged tune-up in my book 335 HP Flathead Ford V-8 Performance Handbook Chapter 6.
Blown Flatheads Forever,
Joe Abbin
505-268-6768
www.blownflathead.com
Roadrunner Engineering - Home - Supercharge Your Ford Flathead
www.blownflathead.com
HOME Featuring books and supercharger kits for Flathead Ford engines. Click on Menu Items to the left to see more.

[Charlie ny]

Ronnie , B&S and everyone following this thread...........
When I setup Joes distributor it was dialed in for 20 degrees total full in at 2500 ,to be on the safe side, big questions in my mind with the blower. Thru a raft of emails , Joe's patience must be mentioned here, things are closing in on success. In place of
a straight limit bushing we are getting ready to use an eccentric bushing. I machined some ecc bushings yesterday that are now winging to New Jersey.
I've decided to do away with the bushing over the limit pin from now on and
develop an adjustable stop so fine tuning can be accomplished an eye lash at a time.
One thing is clear to me.......guys building flatheads these days are investing ,in many
cases, huge bucks and they want and demand top performance.
Charlie ny

[jrvariel48]

I install one of the offset bushings today. I'll let you know what comes of it.

[jrvariel48]

I finally was able to get some time with the car today. I ended up installing a set screw type of adjuster for the timing advance. I was nervous the nylon bushings would fall off. Probably wasn't a problem, but I went with the set screw. So here's what I got and I need the experienced blower guys to kick in also!!
Idle is 4 degrees advanced at 700 rpm. At 1000 rpm I'm at about 12 degrees. 1250 rpm is about 15 degrees and I'm all in at 1450 rpm at 17 degree. Of course this is all based on my TDC being zero.
Isn't 1450 rpm to low for total advance?

As far as Air/Fuel is concerned, at idle I have 19 inches of steady vacuum and I'm showing 12.5 on my afr meter. When I rev the motor, the vacuum drops and the afr leans out. Is that what's supposed to happen?
I took it for a drive and just cruising at about 40 mph on a flat road in 4th gear it seemed lean about 17.1 on the afr meter with about 13 inches of vacuum until I stepped on the pedal and then vacuum drops and it got richer. I drove up my street in 2nd gear and put the pedal to the floor and the motor sounded like it broke up, sort of like what a rev limiter sounds like. I'm not sure if I'm running out of fuel and leaning out because I didn't look at the meter. Any responses at appreciated.
Thank you,
Joe

[Ronnieroadster]

Joe 4 degrees at 700 is a bit low with a modified engine 12 degrees at 1000 is much better everything in at 1450 from my experience is to low I prefer to see total advance in around 2200 at the lowest.
The way you see your advance in so soon will cause a lot of detonation especially with the air fuel readings your seeing that show a lean condition. Maybe good for economy but that's not what I think your looking for with this combination.
When you load the engine in second gear it should pull strong if the carb or carbs are feeding enough gas and the octane is high enough to not cause detonation the power valve and the added enrichment when you get on it are needed to help the engine pull correctly. Remember the blower will deliver lots more CFM to the engine so the fuel delivery needs to be able to deliver enough CFM to make the combination work correctly.
From what you wrote my take is full advance is in to soon and the fuel delivery needs to be looked at. Joe what are you using on top of the blower for carb or carbs?
Ronnieroadster

[jrvariel48]

Ronnie, the set up came with a 600 cfm Holley 4160 that's been boost referenced. Right now it has 68 main jets and a secondary jet plate equal to 69 jets. My engine still has the stock cam and bottom end. Should I change my initial advance? I can put stronger springs in the distributor to increase the time of the advance and up to 2200 rpm. I'm definitely not concerned with fuel economy and I'd rather run rich and lose some power than detonate.

[Ronnieroadster]

Joe the 600 CFM Holley 4160 you have is fine and the jetting is fine also. The air fuel readings you see seem very lean for the carb for some reason that has me confused. Maybe the boost reference power valve has something to do with that. On my street blower motor I don't use a boost reference power valve never felt I needed it.
For primary jetting on my engines I would use between 68 to 72 so your right in the ball park with the jetting especially with the stock cam. But my engines have always been modifed lots more than your combination. However your learning curve on your engine will give you a lot of experiance that maybe in the future you can applly to an engine that has more modifications.
What have you seen for boost readings? The stock cam and ports will be a big restriction to what the blower and carb are able to flow into the cylinders so that also must be considered.
On any stock flatheads I tune I always set the initial at 12 degrees if you do that and work with stronger springs to get the total advance in around 2200 you should see a change. What brand spark plugs are you using and plug gap?
Ron

[jrvariel48]

Ron, I have a short piece of flex pipe installed after the header. The O2 sensor is installed after that and I'm wondering if that has something to do with the lean readings? It's going to be replace with tubing when I can get the car to the my brother in laws shop. I haven't seen more that 2 lbs of boost but I haven't really mashed it in fear of detonation.
I'm using NGK B-6L plugs with a .025 gap.
Are you saying I should set my initial timing to 12 degrees advanced and leave my total where it is for now at 17 degrees?
Thanks for responding, I appreciate the help and knowledge
Joe

[Ronnieroadster]

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Originally Posted by jrvariel48

Ron, I have a short piece of flex pipe installed after the header. The O2 sensor is installed after that and I'm wondering if that has something to do with the lean readings? It's going to be replace with tubing when I can get the car to the my brother in laws shop. I haven't seen more that 2 lbs of boost but I haven't really mashed it in fear of detonation.
I'm using NGK B-6L plugs with a .025 gap.
Are you saying I should set my initial timing to 12 degrees advanced and leave my total where it is for now at 17 degrees?
Thanks for responding, I appreciate the help and knowledge
Joe

Yes Joe try to set the initial at 12 and keep the total at 17 for now. If everything sorts out well I would increase the full to 20 max.
The NGK B-6L is fine but increase the plug gap to .035. The location for my A/F sensor is about 6 inches behind the collector however each exhaust port has a separate runner to the collector this gives a much better reading.
Since you have only seen 2 pounds of boost so far the added power the blower will give you has not been felt yet I'm thinking your combination should put out around 8 pounds. Things start to get exciting when your around 5 pounds. I'm thinking your carb with the jetting and boost reference power valve will work fine with no detonation if the gas you use has a decent octane rating.
Ron

[jrvariel48]

Ok Thank you I'll give that a try!

[Bored&Stroked]

I agree with Ron on the timing - it is coming in too early. I'd aim for a total of about 16 - 18 for now, but have the mechanical portion of it start at about 1000 or so and be all in at about 2000 - 2200 or so RPM. How do you know where you timing is? Did you pull the head and setup TDC and also mark the front pulley with timing marks? How did you measure it?

I can't see the power valve causing the car to be that lean as you're just in a cruise condition and not under heavy load - if it wasn't working right, it would be rich (as it would be open/blown and dumping fuel).

O2 sensor: You have to have a completely sealed exhaust system for the readings to be solid - make sure that there are no leaks before the sensor and that it is at least 12" from the end of the pipe. Any leaks before it and it will show lean.

What type of ignition are you running?

[jrvariel48]

B&S thanks for you input. I used the tyrap method with the head on and then used a dial indicator with the head off. Both gave me the same mark. Is it 100% TDC? I don't know that for certain. They pulley is marked at 0, 4, 15, & 24 degrees advanced for reference. I also used an advance style timing light to zero back the advance. I used the diameter of the pulley divided by 3.14 method and used a caliper to get the marks on the pulley. Again, are they 100%? I did the best I could as carefully as I could double checking everything.
I think the flex pipe is causing the lean condition I'm reading. That will be straighten out when I get the car to my brother in laws shop to install the tubing.
I'm running a chevy points distributor with a set screw to adjust the advance. I ordered springs for the advance
Thanks Joe
.

[jrvariel48]

I'm referencing my "Distributor advance spring" post and I'm wondering what kind of curve I'm shooting for. For example, If I set my initial at 12 degrees @ 700 rpm and my total at let's say 16 degrees @ 2200 rpm what exactly am I shooting for!? Am I correct in saying my curve will be 4 degrees? (16 total minus 12 initial). If I start to see advance at 1000 rpm am I on the right track?
I'm confused

[Ronnieroadster]

Originally Posted by jrvariel48

I'm referencing my "Distributor advance spring" post and I'm wondering what kind of curve I'm shooting for. For example, If I set my initial at 12 degrees @ 700 rpm and my total at let's say 16 degrees @ 2200 rpm what exactly am I shooting for!? Am I correct in saying my curve will be 4 degrees? (16 total minus 12 initial). If I start to see advance at 1000 rpm am I on the right track?
I'm confused

Joe you have it right if you set the initial at 12 degrees at 700 idel RPM when you rev up the engine your checking to see what the crank degree reading is at the higher RPM so if your looking for a total of 16 then you will see that number on the degree wheel at the higher RPM so yes it will increase 4 more degrees from your initial setting at idel. The total advance reading is adjusted by the centrifugal springs and or an adjustable stop not by moving the distributor after your inital setting.
Seeing the advance starting at any point above your initial setting would be accurate the amount you see depends on how heavy the advance weight springs are in the dist.
Ron

[jrvariel48]

Originally Posted by Ronnieroadster

Joe you have it right if you set the initial at 12 degrees at 700 idel RPM when you rev up the engine your checking to see what the crank degree reading is at the higher RPM so if your looking for a total of 16 then you will see that number on the degree wheel at the higher RPM so yes it will increase 4 more degrees from your initial setting at idel. The total advance reading is adjusted by the centrifugal springs and or an adjustable stop not by moving the distributor after your inital setting.
Seeing the advance starting at any point above your initial setting would be accurate the amount you see depends on how heavy the advance weight springs are in the dist.
Ron

Thank you for clarifying that for me Ron. I should be able to get the car out today for some testing

[jrvariel48]

OK, here's where I'm at right now. I have one heavy spring and one medium spring.

850-1500 rpm @ 12 degrees
1600 @ 13 degrees
1700 @ 15
1800 @ 16
1900 @ 17 (total advance)

Is it ok for the motor to be at 12 degrees in the 850-1500 rpm range? If it's not, is there a way to correct that without messing up the higher rpm degrees? Does it matter which spring goes where?

[jrvariel48]

I tried a couple of spring combo's and then made a couple. Here's what the last set did.

12 degrees @ 850-1450 rpm
13 degrees @ 1450
14 degrees @ 1550
15 degrees @ 1600
16 degrees @ 1700
17 degrees @ 2000

I tried mashing the pedal again in 2nd gear and as the rpm rose the motor started to break up again and what sounded like a backfire. I didn't look at my rpm or AF meter because it happened so fast and I immediately backed off the throttle. Anyone?
Thanks

[Pete F]

To start
Get rid of the vacuum advance
Second total advance should happen by 2000 rpms
And third depending on the heads and the compression ratio of the engine will determine where the total advance should end up.
There is no set timing that works for all engines there is a lot of determining factors that go along with the timing like compression , cam , chamber design.
It is going to be a crap shoot of trial and era .
Timing on a blower engine is determined by boost and compression ratio
People try to say that you need to run a certain setting for all blower engines are wrong.
Under driven engines need timing on the bottom to get them to come alive . Just as low compression engines due.
Boost and compression ratio determine the final ratio so if you start out with 6:1 and are under driving the blower 20-30 degrees is not a lot of timing because you are probably ending up with a 11:0 ratio .
I never built street blower engines with less than 8:5 compression because they are lazy and need to much boost which causes overheating.
Since your engine is not at a dyno take your time and listen to the engine under different loads to set the timing and read the plugs .
Speckles mean destination .Good luck!!



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[jrvariel48]

Pete thanks for the input. Vacuum advance is gone. This is an all stock motor running 91 octane fuel. I'm just concerned why the motor sounded like it was breaking up. Is that what detonation sounds like? I'm afraid of destroying a piston or worse.

[Ronnieroadster]

Originally Posted by jrvariel48

Pete thanks for the input. Vacuum advance is gone. This is an all stock motor running 91 octane fuel. I'm just concerned why the motor sounded like it was breaking up. Is that what detonation sounds like? I'm afraid of destroying a piston or worse.

Pete when A flathead has detonation the sound you hear is odd and it comes from the flywheel area of the engine sort of marbles bouncing around. I don't know why but that's were you will hear the sound. However I doubt your experiencing detonation with 91 octane and the advance curve you posted I see no problem at all. Now if you can get the total to 20 degrees eventually that will be better but at 17 that's not so bad. But whatever you do don't go above 25 degrees total advance. If you go above the 25 number then you will experience detonation even in a stock engine especially with pump gas.
Ron

[Pete F]

Originally Posted by jrvariel48

Pete thanks for the input. Vacuum advance is gone. This is an all stock motor running 91 octane fuel. I'm just concerned why the motor sounded like it was breaking up. Is that what detonation sounds like? I'm afraid of destroying a piston or worse.

Pull a couple plugs and read them
If you don't know what your looking at post a picture or send me a picture at my web site.
And you said it's a modified Chevy dist so check the dwell
You may have a bad plug or maybe the dwell is off.
Plugs tell the story
[email protected]


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[jrvariel48]

Originally Posted by Pete F

Pull a couple plugs and read them
If you don't know what your looking at post a picture or send me a picture at my web site.
And you said it's a modified Chevy dist so check the dwell
You may have a bad plug or maybe the dwell is off.
Plugs tell the story
[email protected]


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Pete, the plugs are black and sooty. I checked the condenser and it tests fine. I also checked the plug wires and plugs. I removed the blower belt for now as a fellow barner requested to see if the problem is there. I'm about to fire it up so I can check the dwell and take a test ride.
Thanks, Joe

[jrvariel48]

Originally Posted by Ronnieroadster

Pete when A flathead has detonation the sound you hear is odd and it comes from the flywheel area of the engine sort of marbles bouncing around. I don't know why but that's were you will hear the sound. However I doubt your experiencing detonation with 91 octane and the advance curve you posted I see no problem at all. Now if you can get the total to 20 degrees eventually that will be better but at 17 that's not so bad. But whatever you do don't go above 25 degrees total advance. If you go above the 25 number then you will experience detonation even in a stock engine especially with pump gas.
Ron

Ron, does it sound like pinging like when cars in the 60's and 70's had crappy gas? I'm going for push the advance to 20 degrees today plus perform what I responded to Pete
Thank you, Joe

[jrvariel48]

I checked the condenser, plugs and wires and pushed the advance up to 20 degrees it's all in around 1900+ rpm. I can't get it any higher with the springs I have. I couldn't check the dwell because my meter decided not to work today.
I removed the blower belt and went for a ride. It ran rough like a couple of cylinders weren't firing. It smelled very rich, but I don't know if that has anything to do with it.

[jrvariel48]

Update. I had a fouled plug. Maybe a hotter or cooler plug?
Still getting the popping sound at about 3500 rpm. If I don't mash the pedal to the floor it runs real nice with about 2 pounds of boost and secondaries kicking in. It seems to happen at WOT around 3500 rpm
Thanks

[Ronnieroadster]

Originally Posted by jrvariel48

Update. I had a fouled plug. Maybe a hotter or cooler plug?
Still getting the popping sound at about 3500 rpm. If I don't mash the pedal to the floor it runs real nice with about 2 pounds of boost and secondaries kicking in. It seems to happen at WOT around 3500 rpm
Thanks

Joe I'm thinking that popping sound is being caused by an ignition problem. I gave up on dual points and condensers years ago converted to Pertronix and never looked back. One issue we were having was the condensers were giving us big trouble. When I ran dual points the dwell was important as well as the type of plug wires I used.
Since you found a fouled plug that means the primary jetting is to big for the stock engine or the ignition is not hot enough to fire the plugs in a rich environment. If you feel good about the ignition system that being the coil etc then I would go down two jet sizes and also try a hotter plug. You should see a change and if its for the better I would go down another jet size removing gas a little at a time.
Ron

[Pete F]

So black and sooty plugs will stop the engine from reving and cause all kinds of misfiring .
So here are some things can cause that condition .
1 over jetted carbs
2 float level
3 or retarted timing
I'd go with the timing first
And put the blower belt back on you are not running any crazy boost so dio the problem with it set up the way you are going to run it.


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[Pete F]

Hey one last thing
What plugs are in the engine and please don't tell me platinum plugs because with that ignition you don't have enough spark to run them.
And what gap are you running
I run .028-.032 with a blower or turbo engine.
Keep us posted


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[jrvariel48]

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Originally Posted by Ronnieroadster

Joe I'm thinking that popping sound is being caused by an ignition problem. I gave up on dual points and condensers years ago converted to Pertronix and never looked back. One issue we were having was the condensers were giving us big trouble. When I ran dual points the dwell was important as well as the type of plug wires I used.
Since you found a fouled plug that means the primary jetting is to big for the stock engine or the ignition is not hot enough to fire the plugs in a rich environment. If you feel good about the ignition system that being the coil etc then I would go down two jet sizes and also try a hotter plug. You should see a change and if its for the better I would go down another jet size removing gas a little at a time.
Ron

Ron will that have any effect on the AF mixture? Right now from what I could tell, my numbers are descent. Of course I need to follow them better once I get things ironed out. I'm certainly not opposed to a pertronix set up and ran one in a crab set up which worked perfectly. If it's a hotter spark I need, then I think I should go that route. Which unit should I be looking at? Igniter. 1,2 or 3? Does the advance set up stay the same?
Thank you Joe

[jrvariel48]

Originally Posted by Pete F

So black and sooty plugs will stop the engine from reving and cause all kinds of misfiring .
So here are some things can cause that condition .
1 over jetted carbs
2 float level
3 or retarted timing
I'd go with the timing first
And put the blower belt back on you are not running any crazy boost so dio the problem with it set up the way you are going to run it.


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Pete I think my timing is ok and agree with Ron about the spark not being hot enough. I'm running NGK BL6 plugs. Right now they're gapped at 35. They were at 25. I haven't been able to see a difference yet with the problem I'm currently having.
Thank you Joe

[Pete F]

I just read back and saw you have a 600 Holley on this engine .
Since parts are readily available for a 600 I would see what the idle vacuum is and check the power valve for the proper setting of a blown diaphragm because if you don't have a blow back valve in the base of that carb one backfire will have blown the valve and that will cause the black plugs for sure.
And if that engine is stock I would be looking for 390 four barrel.


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[jrvariel48]

The power valve is boost referenced, I'll have to check it. The carb came with the blower and intake and its what they recommend for this set up

[Ronnieroadster]

Originally Posted by jrvariel48

Ron will that have any effect on the AF mixture? Right now from what I could tell, my numbers are descent. Of course I need to follow them better once I get things ironed out. I'm certainly not opposed to a pertronix set up and ran one in a crab set up which worked perfectly. If it's a hotter spark I need, then I think I should go that route. Which unit should I be looking at? Igniter. 1,2 or 3? Does the advance set up stay the same?
Thank you Joe

Joe the A/F reading your seeing should be used as a reference only. Since you see soot on the plugs that tells me its still to fat with gas. Im thinking if you lean it out a bit the plugs should improve in color also since your using NGK the B-6L is a cold plug you can try the B-4L that will also help since its the hotter plug. Converting to Pertronix I would go with the standard Ignitor which is the 1 that will work fine for your combination also use the correct coil and the correct plug wires so it all works correctly.
Ron

[Bored&Stroked]

Okay - might as well jump in again . . . this is a regular "tuning party"! LOL

1) Reading Plugs: You can't run the engine under load, take your foot off the gas, idle around a bit and then look at your plugs - they will almost always be sooty if you do this. You need to run the engine under load, shut it off, push the clutch in (so you're not washing down the plugs) and then check the plugs. This will give you a much better coloring . . . though I will say, that it is much harder to read plugs with todays fuels, then in the 'old days'.

2) Carb: What rating is your power valve? You should check your vacuum at idle (below the blower) and an approximate PV number is to take the vacuum and divide it by 2. My guess, about a 5.5 - 6.5 or so would work. Also, the place you pull your 'boost referencing' from is below the blower (kind of the whole point).

3) Carb Size: Given that you're running a stock cubic inch engine, with no real internal mods, I believe you've got a LOT more carb than that engine can use. With an over-sized carb, you can usually gradually run the engine up, but if you rapidly open the throttles, then the vacuum drops too far/fast and the volume of air isn't there to keep the air velocity up to correctly atomize the fuel. It will tend to bog really badly, until the RPMs creep back up. I truly believe you'd be much better off with a 390 Holley.

4) Ignition: Charlie knows how to build an ignition and given your boost levels and RPM, it should work just fine (and it sounds like you have the advance curve and max-advance setup about right). Couple questions:

a) What amount of initial timing are you running?
b) What are the total degrees of distributor advance (mechanical).
c) Your number of 20 degrees - was that TOTAL advance (both of the above).
d) Given your low boost levels, I think that 20 degrees won't hurt you. If you get to higher boost levels (like 6 lbs), you'll probably need to take a couple degrees back out.

4) O2 Sensor: Did you fix your exhaust as what type of readings are you seeing as you gently roll the throttle and when you rapidly open it?

Keep the information coming!

D

[jrvariel48]

Originally Posted by Ronnieroadster

Joe the A/F reading your seeing should be used as a reference only. Since you see soot on the plugs that tells me its still to fat with gas. Im thinking if you lean it out a bit the plugs should improve in color also since your using NGK the B-6L is a cold plug you can try the B-4L that will also help since its the hotter plug. Converting to Pertronix I would go with the standard Ignitor which is the 1 that will work fine for your combination also use the correct coil and the correct plug wires so it all works correctly.
Ron

Thank you Ron. What's your thoughts on a 390 carb? Listening to B&S and others, has me thinking about my next step. Can the 600 be jetted down enough to be effective or am I beating a dead horse?

[jrvariel48]

Originally Posted by Bored&Stroked

Okay - might as well jump in again . . . this is a regular "tuning party"! LOL

1) Reading Plugs: You can't run the engine under load, take your foot off the gas, idle around a bit and then look at your plugs - they will almost always be sooty if you do this. You need to run the engine under load, shut it off, push the clutch in (so you're not washing down the plugs) and then check the plugs. This will give you a much better coloring . . . though I will say, that it is much harder to read plugs with todays fuels, then in the 'old days'.

2) Carb: What rating is your power valve? You should check your vacuum at idle (below the blower) and an approximate PV number is to take the vacuum and divide it by 2. My guess, about a 5.5 - 6.5 or so would work. Also, the place you pull your 'boost referencing' from is below the blower (kind of the whole point).

3) Carb Size: Given that you're running a stock cubic inch engine, with no real internal mods, I believe you've got a LOT more carb than that engine can use. With an over-sized carb, you can usually gradually run the engine up, but if you rapidly open the throttles, then the vacuum drops too far/fast and the volume of air isn't there to keep the air velocity up to correctly atomize the fuel. It will tend to bog really badly, until the RPMs creep back up. I truly believe you'd be much better off with a 390 Holley.

4) Ignition: Charlie knows how to build an ignition and given your boost levels and RPM, it should work just fine (and it sounds like you have the advance curve and max-advance setup about right). Couple questions:

a) What amount of initial timing are you running?
b) What are the total degrees of distributor advance (mechanical).
c) Your number of 20 degrees - was that TOTAL advance (both of the above).
d) Given your low boost levels, I think that 20 degrees won't hurt you. If you get to higher boost levels (like 6 lbs), you'll probably need to take a couple degrees back out.

4) O2 Sensor: Did you fix your exhaust as what type of readings are you seeing as you gently roll the throttle and when you rapidly open it?

Keep the information coming!

D

Thanks for responding!
Reading plugs:
That's the way we do it with bikes. We call it throttle chopping. I can check that this weekend if it don't rain!
Carb:
My power vale is a 4.5. Primary jets-68. Secondary jet plate-69. I'll check the vac this weekend. Right now my gauge is coming from the carb spacer between the carb and the blower. Yes boost ref. is being pulled from under the blower.
Carb size:
Understood. I'm not familiar with the 390 at all. Would I be looking for a new unit or rebuilt? Anyone on the barn?
Ignition:
Charlie has been extremely helpful AND patient through the whole process!!! I'm sure he has better things to do than answer my silly questions!
Questions:
a) 12 degrees
b) 8 degrees
c) yes
d) ok
O2 sensor:
I have not been to the shop yet. I've been working 14 hours days most of the week. Killing me!
I'll also try that this weekend. I tried to Gopro a video last week bit it came out bad.

Thank you everyone for taking time to help!!It's much appreciated!
Joe

[Ronnieroadster]

Originally Posted by jrvariel48

Thank you Ron. What's your thoughts on a 390 carb? Listening to B&S and others, has me thinking about my next step. Can the 600 be jetted down enough to be effective or am I beating a dead horse?

Joe my experience with the 390 has shown me a number of times on cars I have worked on with that small carb its to small for most flathead applications and in my opinion yours included. I would jet the 600 down a bit and work on the Pertronix and go to the hotter NGK plug. Also the latest issue of Hot Rod magazine has an excellent article about ignition timing its good reading.
Ron

[jrvariel48]

Originally Posted by Ronnieroadster

Joe my experience with the 390 has shown me a number of times on cars I have worked on with that small carb its to small for most flathead applications and in my opinion yours included. I would jet the 600 down a bit and work on the Pertronix and go to the hotter NGK plug. Also the latest issue of Hot Rod magazine has an excellent article about ignition timing its good reading.
Ron

Sounds like a cheaper alternative for sure! I'll check out the article!
A coworker of mine used to tune top fuel cars and told me to try leaving the window open partially on the distributor because sometimes they could get pressurized and that could cause the spark scatter?? Did you ever hear of anything like that? I mean, it doesn't hurt to try it, lol!!

Should I jet down the secondaries also?
Thanks, Joe

[Ronnieroadster]

Joe the secondary's being a metering plate would be more of a challenge to go smaller I would imagine plates with smaller holes would be available. But for now I would leave that alone on your carb.
When I ran my 671 GMC blower I used two Holley 600 carbs on top of the blower same carb you have. The blower was on top of my 258 cube flathead which I drove on the street for a very long time I left the metering plates in the carbs. When I started using the set up in my race car I converted the secondary's to jets by using Quick Fuel Technology conversion plate. Doing that I was able to run 76 jets in the secondary and 72 primary's. That little 258 flahtead last year went 179 MPH in my rear engine modified roadster with a little work a small cube flathead will make big power. The spark scatter idea might be valid especially with a high output ignition its worth a try leaving the door open a bit.
Ron

[Bored&Stroked]

Hey - why not put some additional tuning into the 600 and see if you can make it work - definitely worth a try (you already have the carb). If that doesn't work and you still have the same problem, then it is either NOT the carb . . . or maybe try another carb. It is always a process of problem identification along with some trial and error. Ronnie has you covered on the 600 - he's ran them a lot and I hope it works out for yah! Best of luck.

[jrvariel48]

Originally Posted by Bored&Stroked

Hey - why not put some additional tuning into the 600 and see if you can make it work - definitely worth a try (you already have the carb). If that doesn't work and you still have the same problem, then it is either NOT the carb . . . or maybe try another carb. It is always a process of problem identification along with some trial and error. Ronnie has you covered on the 600 - he's ran them a lot and I hope it works out for yah! Best of luck.

Thanks B&S! I don't know if you read my question about putting a hole in the distributor cap a couple of posts back, but I'm going to try that first. Then on to the carb and ignition. I appreciate your responses, thank you, Joe

[jrvariel48]

Doing a little tinkering today. I installed the NGK B-4L with a .025 gap today and removed the window from the distributor. When I reached about 3000 rpm there was no backfiring this time, it just felt under powered. I also noticed my AF meter lean out off the chart, but I still haven't removed the flex pipe so I don't know if that's a factor yet. I'm going to try a little longer cruise so I can get some video of the AF meter

[Bored&Stroked]

You cannot trust the AFR meter if you don't have a correctly installed and sealed O2 sensor in the exhaust system. It should be at least 18" back from the third (rear) exhaust port, should be installed at an angle (to keep water off of it) and there needs to be enough pipe AFTER it to not let oxygen from the outside mess with the readings. There cannot be any leaks in the system before the O2 sensor - or you'll get too lean of readings.

[jrvariel48]

Originally Posted by Bored&Stroked

You cannot trust the AFR meter if you don't have a correctly installed and sealed O2 sensor in the exhaust system. It should be at least 18" back from the third (rear) exhaust port, should be installed at an angle (to keep water off of it) and there needs to be enough pipe AFTER it to not let oxygen from the outside mess with the readings. There cannot be any leaks in the system before the O2 sensor - or you'll get too lean of readings.

It's in the right spot and at the right angle now if I just had time to get to the shop to get the flex pipe out! I think I'll stop testing until I nail that down so I can tell what's really happening. Thank, Joe

[Pete F]

Have you checked the power valve yet to see if it's blown out or what vacuum reading it's for.
A blown power valve richens the mixture unbelievable !!
And if you can read boost I'm sure you can read vacuum to verify thAt you have the proper one in!


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[jrvariel48]

Originally Posted by Pete F

Have you checked the power valve yet to see if it's blown out or what vacuum reading it's for.
A blown power valve richens the mixture unbelievable !!
And if you can read boost I'm sure you can read vacuum to verify thAt you have the proper one in!


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Pete, I checked and I had 18 in's of vacuum at the manifold at 800 rpm. I was going to try an 8.5 PV in there because right now I have a 4.5 PV. I didn't check the PV that's in there presently to see if it's NG. Is there a way to check it with the motor running? At this point, I think I'll wait to get the exhaust sealed up before I do anymore testing so I know what's going on.
Thanks, Joe

[Pete F]

Originally Posted by jrvariel48

Pete, I checked and I had 18 in's of vacuum at the manifold at 800 rpm. I was going to try an 8.5 PV in there because right now I have a 4.5 PV. I didn't check the PV that's in there presently to see if it's NG. Is there a way to check it with the motor running? At this point, I think I'll wait to get the exhaust sealed up before I do anymore testing so I know what's going on.

Thanks, Joe

Joe if you have 18" of vacuum you can put a 10.5 valve in and jet down the main jets if it's rich.
Also what color spring is in the secondary's since you have a stock engine and ignition you can't get to aggressive with the secondary's .
Have you checked the float levels
I set the primary just below the hole and the secondary just above the hole. And Holley carbs should run 7 psi fuel pressure they are not like Holley 94's or Strombergs they will take the fuel pressure!!


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[jrvariel48]

Originally Posted by Pete F

Joe if you have 18" of vacuum you can put a 10.5 valve in and jet down the main jets if it's rich.
Also what color spring is in the secondary's since you have a stock engine and ignition you can't get to aggressive with the secondary's .
Have you checked the float levels
I set the primary just below the hole and the secondary just above the hole. And Holley carbs should run 7 psi fuel pressure they are not like Holley 94's or Strombergs they will take the fuel pressure!!


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Right now I have both float levels set at the hole. I'm not sure on the spring. I haven't got that far yet! I'll have to open it up. I can adjust the fuel pressure up, I'm at 6 now.
Thanks!

[Pete F]

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Originally Posted by jrvariel48

Right now I have both float levels set at the hole. I'm not sure on the spring. I haven't got that far yet! I'll have to open it up. I can adjust the fuel pressure up, I'm at 6 now.

Thanks!

5-7 is fine for fuel pressure but the primary fuel level you want just below the hole.
If you want to try an easy test wire the secondary's closed and try the car at least you can tell if the primaries are rich or lean than after that go to the secondary's


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[jrvariel48]

Originally Posted by Pete F

5-7 is fine for fuel pressure but the primary fuel level you want just below the hole.
If you want to try an easy test wire the secondary's closed and try the car at least you can tell if the primaries are rich or lean than after that go to the secondary's


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Thanks will do!

[jrvariel48]

I was able to get some work done the last couple of weeks. I got rid of the flex pipe and welded in hard pipe and installed a new O2 sensor. When I pulled out the old sensor, I saw the threads were damaged. Here's what I have so far for my timing with the help of Charlie sending me a bag of assorted springs! Thanks Charlie! I went with the advise of Joe Abbin on my intial advance of 4 degrees for now. I also went with RonnieRoadster's advice and installed a Pertronix set-up including wires. I went with PeteF's advise on the power valve. Right now I started with an 8.5 and jetted down the primary's from 68 to 66 for a starting point. I also found the secondary float was stuck so that may have explained the lean condition at WOT. I installed a quick change vacuum secondary spring set up and found a natural spring in there. I purchased the spring kit so I can tune accordingly. At idle, my A/F reading was 11.0. As I drove, I noticed it richen up when the power valve kicked in. I didn't get a lot of good info at cruise as the streets here are short and I didn't want to go too far from home in case something went wrong. When I mashed the pedal, the lean condition was gone and the A/F was around 12.5. I didn't look at the boost, but the motor pulled very nicely! I think I have a good starting point now with the help of everyone here. Let me know what you think of the numbers and I'll try to get some more info as soon as I can. Thanks to all that helped!
RPM DEGREES
750 4
1000 7
1200 9
1400 11
1550 12
1700 13
1900 14
2000 15
2200 16

[Ronnieroadster]

Very nice Joe now that you have the motor pulling nicely all that's left is a little fine tuning which im sure you can now handle. The advance cure looks good and safe. If you discover she runs a touch warm on the open road I would look into getting the total as close to 20 as possible but for now drive the car and see how the temps are. The secondary float issue was certainly a major cause of all your troubles. With everyone helping with ideas and the various changes you were able to accomplish now you can feel good about tuning and moving forward on your combination. Very Very Good.

[jrvariel48]

Originally Posted by Ronnieroadster

Very nice Joe now that you have the motor pulling nicely all that's left is a little fine tuning which im sure you can now handle. The advance cure looks good and safe. If you discover she runs a touch warm on the open road I would look into getting the total as close to 20 as possible but for now drive the car and see how the temps are. The secondary float issue was certainly a major cause of all your troubles. With everyone helping with ideas and the various changes you were able to accomplish now you can feel good about tuning and moving forward on your combination. Very Very Good.

Thanks Ronnie, couldn't have done this without your help and the help of others!
This post isn't dead yet. Hopefully I could get some pointers on what to do with the carb and the A/F numbers I come up with.
Thanks, Joe

[Bored&Stroked]

Great news! Sounds like you found the big source of it going lean and stumbling as a result. I'm with Ron - once you get a little more seat time in it, you might advance it about 2 degrees at a time, just to see how she performs.

Keep driving it and watching your AFR readings - so you get a really good feel for where they are at under different conditions. Given that you're not running much boost, you'll probably be able to lean it out a bit in the secondaries . . . getting the AFR closer to 13.1 to one (or a bit more). I wouldn't go much leaner than that.

You'll need to take it on some longer routes to see what the AFR is at in different cruise and load conditions - to see whether or not you need to go leaner in the primaries as well. Just don't move too many jet sizes at a time - in any direction! I don't remember if you have one, but a vacuum gauge is a pretty handy tool to have as well.

[jrvariel48]

Originally Posted by Bored&Stroked

Great news! Sounds like you found the big source of it going lean and stumbling as a result. I'm with Ron - once you get a little more seat time in it, you might advance it about 2 degrees at a time, just to see how she performs.

Keep driving it and watching your AFR readings - so you get a really good feel for where they are at under different conditions. Given that you're not running much boost, you'll probably be able to lean it out a bit in the secondaries . . . getting the AFR closer to 13.1 to one (or a bit more). I wouldn't go much leaner than that.

You'll need to take it on some longer routes to see what the AFR is at in different cruise and load conditions - to see whether or not you need to go leaner in the primaries as well. Just don't move too many jet sizes at a time - in any direction! I don't remember if you have one, but a vacuum gauge is a pretty handy tool to have as well.

Thanks for your help B&S! I do have a vacuum gauge right next to the A/F gauge. I should be able to get some driving time this weekend and I'll report my findings. Thanks Joe

[jrvariel48]

I was able to do a little more fine tuning on the timing last night. I should be able to get out tomorrow for some better A/F readings.
Here's what I have after last night.
RPM'S Degrees
750 4
920 5
1000 6
1080 7
1120 8
1240 9
1270 10
1360 11
1520 12
1780 13
1950 14
2110 15
2340 16
2580 17

The rpm numbers are very close. I took my time and checked it twice using a digit timing light where I could dial in the degrees and then carefully rpm the motor up to my 0 timing mark. It's the best I could do with what I have.
Please comment on what you see. I know every motor is different, but I'd like to know what others may have if it's been recorded.
Thanks, Joe

[jrvariel48]

I got a little drive time today.
So cruising on a flat road at 60 mph in 5th gear at 1800 rpm's, the A/F gauge seems to vary from 12.1 to 13.0 with a steady 10 inches of vacuum.
When I put it to the floor and up to 4 lbs of boost the A/F was 14.4
Going up a big hill and maintaining 60 mph, A/F was from 12.8 to 13.4, vacuum was at 3 inches so I had my foot in it but the secondaries weren't open.
I did a video while holding my phone. Next time out, I'll have my Gopro on the A/F and vacuum gauges, while I try to record the rpm and boost.

Please comment! Thanks, Joe

[Charlie ny]

Joe,
You are what this hobby is all about.
Did you down shift or was the hill in 5th. Keep in mind modern cars unblown
or blown with automatic trans probably drop down 2 or 3 gears to clear a big hill. 221
cubes is low on the omph scale. Keep in mind your brain is the computer controlling
your motor.
Charlie ny

[jrvariel48]

Originally Posted by Charlie ny

Joe,
You are what this hobby is all about.
Did you down shift or was the hill in 5th. Keep in mind modern cars unblown
or blown with automatic trans probably drop down 2 or 3 gears to clear a big hill. 221
cubes is low on the omph scale. Keep in mind your brain is the computer controlling
your motor.
Charlie ny

Thanks Charlie! Couldn't have done it without your unwavering assistance! Much appreciated!
I did not downshift. The car just climbed right up the hill with a little throttle. I can tell you before the blower was installed, I had to downshift to 4th gear and keep the pedal to the floor to make it up that hill. I was very surprised at how nicely it pulled itself up!

[Bored&Stroked]

I think your primaries are fine - in that you were in the 12 to 13.5 range. The only part that I don't like is that when you were under full throttle, that you were are 14.4 with boost (did you stay in it a bit to see if that held? Were you in a higher gear - 4th or 5th?). That is a bit too lean in my mind - even for a NA car.

What did the vacuum do under full throttle? Were you low enough to open the power valves? If so, then I would richer up the secondaries a bit - to get down to no more that 13.5 under boost. If the power valves aren't opening, then you'd go UP in the vacuum number so they open sooner . . . if they are opening, then you'd probably want to change the secondary jets one number and then see where the AFR goes too. Good work on everybody's part!

[jrvariel48]

Thanks B&S. I didn't stay in it. I put the pedal to the floor in fifth gear going about 50 mph until I reached 4lbs and then released the pedal. I can certainly do it again! The vacuum gauge shows the vacuum completely dropping out at WOT. The power valve is an 8.5 and I can say it's opening because when I'm cruising and push the pedal down to drop vacuum, the A/F definitely shows it richen up. I'm assuming that's what I'm seeing
Thanks, Joe

[jrvariel48]

Also, I ordered a Holley conversion kit to get rid of the secondary jet plates which were equal to 67 jets. I have 68, 69 & 70 jets to try.
Should I start with the 68?
Thanks, Joe

[V8COOPMAN]

I will say that everything in that engine compartment is mighty tidy looking! DD

[Pete F]

Originally Posted by jrvariel48

Also, I ordered a Holley conversion kit to get rid of the secondary jet plates which were equal to 67 jets. I have 68, 69 & 70 jets to try.
Should I start with the 68?
Thanks, Joe

Joe
What cfm is that carb?
And what color secondary spring is in the camber?


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[jrvariel48]

Originally Posted by Pete F

Joe
What cfm is that carb?
And what color secondary spring is in the camber?


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Pete, Thanks for you help and suggestions! it's a 600 cfm Hollet 4160 with a natural (no paint) spring.
Thanks Joe

[jrvariel48]

Originally Posted by V8COOPMAN

I will say that everything in that engine compartment is mighty tidy looking! DD

Thanks V8! I really like a stock look with painted heads and not a lot of shiny stuff. I wanted it to look like exactly what it is.. a stock motor with a blower!

[V8COOPMAN]

Originally Posted by jrvariel48

Thanks V8! I really like a stock look with painted heads and not a lot of shiny stuff. I wanted it to look like exactly what it is.. a stock motor with a blower!

I can appreciate the "stock w/blower" idea, but I was specifically speaking of the orderly and purposeful look of the way you have assembled ALL bits 'n pieces...........just NICELY done! DD

[Pete F]

Joe do you think the secondary's are coming in at the proper time??
I still say wire the secondary's closed and jet the primaries first and than add the secondary's in.
At least if you know the fuel mixture is right with the primaries when you add in the secondary's you can jet the knowing the primaries fuel mixture is right.
And if you want the secondary's to come in sooner or later you can change the spring.


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[jrvariel48]

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Originally Posted by V8COOPMAN

I can appreciate the "stock w/blower" idea, but I was specifically speaking of the orderly and purposeful look of the way you have assembled ALL bits 'n pieces...........just NICELY done! DD

Thank you!

[Bored&Stroked]

Originally Posted by jrvariel48

Also, I ordered a Holley conversion kit to get rid of the secondary jet plates which were equal to 67 jets. I have 68, 69 & 70 jets to try.
Should I start with the 68?
Thanks, Joe

Good that you're putting the secondary metering block in - just so much easier to tune. I would start with 68's. Does the new metering block have a power valve or not? (I can't remember?). If so, I would run the same power-valve as you had in the front - or, you can block it off and just use the jets to control the final AF ratio. When you first do the conversion, just pay really close attention to when the boost comes on as to your AF ratio -- just to make sure it isn't going too lean (then just get back out of it).

You're surely getting to know the carb, the tune and the engine - that is what this is all about! Great stuff!

[jrvariel48]

Originally Posted by Bored&Stroked

Good that you're putting the secondary metering block in - just so much easier to tune. I would start with 68's. Does the new metering block have a power valve or not? (I can't remember?). If so, I would run the same power-valve as you had in the front - or, you can block it off and just use the jets to control the final AF ratio. When you first do the conversion, just pay really close attention to when the boost comes on as to your AF ratio -- just to make sure it isn't going too lean (then just get back out of it).

You're surely getting to know the carb, the tune and the engine - that is what this is all about! Great stuff!

Thanks B&S. there is no power valve. I'll start with the 68's and see what happens. Tuning is very interesting. I couldn't imagine doing it without an AF meter!

[jrvariel48]

Originally Posted by Pete F

Joe do you think the secondary's are coming in at the proper time??
I still say wire the secondary's closed and jet the primaries first and than add the secondary's in.
At least if you know the fuel mixture is right with the primaries when you add in the secondary's you can jet the knowing the primaries fuel mixture is right.
And if you want the secondary's to come in sooner or later you can change the spring.


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Pete, I think the secondaries are coming in at the right time? I'll need a little more time behind the wheel to really tell, but I'm thinking they're ok. I also think my primary jets are in a good spot at the moment. Your suggestion with the power valve seems to working great. When I start to put the pedal down, I watch my vacuum gauge drop and the AF gauge, which are right next to each other. I see it richen up right as the vacuum drops below the 8.5 the PV is set for. At that point, I don't think the secondaries are coming in yet, so I'm just seeing the enriching from power valve. Do the secondary vacuum springs have an approximate vacuum number tied to them. Example, at what vacuum does a natural spring come in or start to work? I don't know if it works like a power valve or not.
Thanks for your input Joe

[Talkwrench]

Natural [standard] spring should be 6.5

[scooder]

Where is your vacuum gauge plumbed in? Under carb or under blower?
Is it a combination boost/vacuum gauge? Sounds like it as you stated vacuum goes as soon as boost comes in.
If it is it would be nice if you could plumb a vacuum gauge in under the carb and test drive.
There is a situation where you can see boost under the blower but vacuum under the carb, this can shut the power valve.
I'm asking as you're air/fuel is going leaner under boost, this can be solved by boost referencing the power valve, not sure if this has been covered yet.
Martin.

[jrvariel48]

Originally Posted by Talkwrench

Natural [standard] spring should be 6.5

Thanks Talkwrench! Good info to go by!

[jrvariel48]

Originally Posted by scooder

Where is your vacuum gauge plumbed in? Under carb or under blower?
Is it a combination boost/vacuum gauge? Sounds like it as you stated vacuum goes as soon as boost comes in.
If it is it would be nice if you could plumb a vacuum gauge in under the carb and test drive.
There is a situation where you can see boost under the blower but vacuum under the carb, this can shut the power valve.
I'm asking as you're air/fuel is going leaner under boost, this can be solved by boost referencing the power valve, not sure if this has been covered yet.
Martin.

Thanks Martin. I'm using separate gauges. The vacuum gauge is under the carb and the boost gauge is coming from the intake manifold. I can get the vacuum to drop without any boost coming in if I'm part throttle cruising. At exactly what point, I'm not sure yet because I just don't have the driving time in yet. My power valve is an 8.5 and is boost referenced.
I need to do some testing to see as I start to make boost, where my vacuum is. I know that in WOT, producing 4 lbs of boost I was showing leaner numbers around 14.4. Again, it's hard to tell exactly what's going on yet. I just need to get the time to drive!!
Thanks, Joe

[Pete F]

Hi Joe
The secondary's open on air flow through the primary Venturi
With the blower everything changes so it is going to be trial and era.
I like the secondary's to come in at about half throttle but that's a matter of preference.
If you have the spring selection try a green spring that usually end up being my go to spring .
Than you can try one up or one done like a white or natural but the one thing I always do is loose the check ball that's in the chamber.
Have fun
Pete


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[Pete F]

Joe
14.4 is way to lean under boost I would fatten up the secondary's
You are not looking for fuel economy your looking for performance, that being said afr should be around 12.7-13.2 on WOT.
You would hate to have melted piston.


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[jrvariel48]

Originally Posted by Pete F

Joe
14.4 is way to lean under boost I would fatten up the secondary's
You are not looking for fuel economy your looking for performance, that being said afr should be around 12.7-13.2 on WOT.
You would hate to have melted piston.


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Definitely not looking for fuel economy and that would be bad!! Do you know anything about Holley jet plates?? I installed the jet conversion kit today on my 4160, but I'm confused on reading the jet plate number.
Here's my dilemma. Looking at the jet plate there are numbers cast in the bottom.
"34R-9716B
3
Then there's a number stamped into the middle of the plate. This is where the confusion starts. I looked the number up in the instruction manual and it says a "6" equals a 69 jet. So I installed a 70 jet to test with. When I went on line to check this out, every picture of a jet plate that I saw had the stamped number upside down!! I called Holley tech and the told me it should be read right side up.
If it's a "9" then I just jumped from a 67 jet to a 70. Is there a way to tell what the old jet plate actually is??
Thanks,
Joe

[jrvariel48]

Must've been a 69 jet plate because I test drove it last night with the 70's and there wasn't much of a difference. I'm going back to the 68's in the primary also because I think I'm still a little lean at cruise at about 15.6

[jrvariel48]

I just went through the video from last nights ride. I'm finding that in 5th gear, with light throttle, between 13-16 in. of vacuum, I'm between 15 and 15.6 A/F. I'm also leaning out at 3 lbs of boost, WOT at about 14.5 A/F and rising. It's obviously wanting more fuel!
Plan:
Increase primary jets from 66 to 68
Increase secondary jets from 70 to 72
Increase power valve 8.5 to 10.5
And see how that goes. I may change the vac secondary spring to purple, which in the next size down from natural in my kit.

[jrvariel48]

Originally Posted by Pete F

Hi Joe
The secondary's open on air flow through the primary Venturi
With the blower everything changes so it is going to be trial and era.
I like the secondary's to come in at about half throttle but that's a matter of preference.
If you have the spring selection try a green spring that usually end up being my go to spring .
Than you can try one up or one done like a white or natural but the one thing I always do is loose the check ball that's in the chamber.
Have fun
Pete


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Hey Pete, I don't have a green spring in my kit.
My lightest is white, then there's two different yellows which they describe at lighter and light. Purple is medium light. Plain is medium, which is what I have in there now. Then brown and black. I'm thinking of throwing the purple in there to see what it does.
Thanks,
Joe

[Pete F]

Joe
If you have no hesitation go for the light yellow spring,if you feel the secondary's are coming in to soon go for the purple.
If the afr ratio stays around 14.1 I would go two jet sizes bigger on the secondary's and see if the ratio drops into the 13's
Good luck


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[jrvariel48]

I just install 68 primary jets, 72 secondary jets, a 10.5 in. power valve and a purple vacuum secondary spring. Hopefully, I'll get a chance to take it for a ride tomorrow after work! If I do, I'll post the results.

[Pete F]

Originally Posted by jrvariel48

I just install 68 primary jets, 72 secondary jets, a 10.5 in. power valve and a purple vacuum secondary spring. Hopefully, I'll get a chance to take it for a ride tomorrow after work! If I do, I'll post the results.

Nothing ventured nothing gained!!


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[jrvariel48]

I think I finally got a good tune on the carb! I'd like to hear what everyone thinks.
I have 72 jets in the primary, 76 jets in the secondary, a 10.5 in. power valve and a purple vacuum secondary spring.
At wide open throttle, as boost starts to come in, the air/fuel ratio is about 13.3.
As the boost rises to 3 lbs., it gets a little richer at 12.6
When I'm cruising in 5th gear, 65 mph, around 2000 rpm, depending on my foot, I'm getting readings of 12.9-15.3. Of course, it gets richer as I apply more throttle.
Uphill in 5th gear,half throttle, 4 barrels in and 1.5-2 lbs. of boost, I'm at 11.9-12.6
I can hear the 4 barrels come in at about half throttle.
This is with 91 octane.
Is there anything else I should be looking for?
Thanks, Joe

[Ronnieroadster]

Originally Posted by jrvariel48

I think I finally got a good tune on the carb! I'd like to hear what everyone thinks.
I have 72 jets in the primary, 76 jets in the secondary, a 10.5 in. power valve and a purple vacuum secondary spring.
At wide open throttle, as boost starts to come in, the air/fuel ratio is about 13.3.
As the boost rises to 3 lbs., it gets a little richer at 12.6
When I'm cruising in 5th gear, 65 mph, around 2000 rpm, depending on my foot, I'm getting readings of 12.9-15.3. Of course, it gets richer as I apply more throttle.
Uphill in 5th gear,half throttle, 4 barrels in and 1.5-2 lbs. of boost, I'm at 11.9-12.6
I can hear the 4 barrels come in at about half throttle.
This is with 91 octane.
Is there anything else I should be looking for?
Thanks, Joe

Hi Joe
Its been a while since I have looked at your post been to busy setting records at Speedweek on the Salt Flats 216.131 MPH then let my son really get on the car 225.003 MPH but now I'm back on line looking at stuff. In my opinion what you have posted is really good your primary jet size is exactly what I run using that size carb the air fuel readings are fine I see no reason for any concern. As you posted your not looking for economy just a good running combination that's safe and with reliability I feel you have accomplished your goal. Adding to that you have also learned how to tune the combination so in the future you can help guide others when needed.
Ronnieroadster

[jrvariel48]

Originally Posted by Ronnieroadster

Hi Joe
Its been a while since I have looked at your post been to busy setting records at Speedweek on the Salt Flats 216.131 MPH then let my son really get on the car 225.003 MPH but now I'm back on line looking at stuff. In my opinion what you have posted is really good your primary jet size is exactly what I run using that size carb the air fuel readings are fine I see no reason for any concern. As you posted your not looking for economy just a good running combination that's safe and with reliability I feel you have accomplished your goal. Adding to that you have also learned how to tune the combination so in the future you can help guide others when needed.
Ronnieroadster

CONGRATULATIONS RONNIE!!! I read the post and I was totally blown away!! (no pun intended) That is an accomplishment that goes down in history! Well done! I appreciate the kind words, but I couldn't have done it without your help and the help of others. I also feel that I learned a lot and I'm no longer afraid to jump into something I'm not familiar with. I'm far from having a perfect tune up, but I definitely feel the improvement in the motor and I think this will be just fine for my type of driving.
Thanks again,
Joe