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Old 07-03-2017, 11:40 AM   #41
jrvariel48
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Default Re: Vacuum signal

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
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Old 07-03-2017, 02:58 PM   #42
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Default Re: Vacuum signal

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?
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Old 07-03-2017, 03:16 PM   #43
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Default Re: Vacuum signal

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.
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Old 07-03-2017, 05:09 PM   #44
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Default Re: Vacuum signal

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
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Old 07-04-2017, 08:11 AM   #45
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Default Re: Vacuum signal

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
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Old 07-04-2017, 10:20 AM   #46
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Default Re: Vacuum signal

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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.
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Old 07-04-2017, 12:05 PM   #47
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Default Re: Vacuum signal

Ok Thank you I'll give that a try!
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Old 07-05-2017, 06:57 AM   #48
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Default Re: Vacuum signal

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?
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Old 07-05-2017, 11:23 AM   #49
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Default Re: Vacuum signal

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
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Old 07-07-2017, 06:00 PM   #50
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Default Re: Vacuum signal

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
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Old 07-07-2017, 07:13 PM   #51
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Default Re: Vacuum signal

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Originally Posted by jrvariel48 View Post
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
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Old 07-08-2017, 05:10 AM   #52
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Default Re: Vacuum signal

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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
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Old 07-08-2017, 11:52 AM   #53
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Default Re: Vacuum signal

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?
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Old 07-08-2017, 03:27 PM   #54
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Default Re: Vacuum signal

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
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Old 07-08-2017, 04:29 PM   #55
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Default Re: Vacuum signal

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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Old 07-08-2017, 06:02 PM   #56
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Default Re: Vacuum signal

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.
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Old 07-08-2017, 06:20 PM   #57
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Default Re: Vacuum signal

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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
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Old 07-08-2017, 07:04 PM   #58
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Default Re: Vacuum signal

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Originally Posted by jrvariel48 View Post
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
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Old 07-09-2017, 10:54 AM   #59
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Default Re: Vacuum signal

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Originally Posted by Pete F View Post
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
pandpvintagerepair@gmail.com


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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
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Old 07-09-2017, 10:59 AM   #60
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Default Re: Vacuum signal

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Originally Posted by Ronnieroadster View Post
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
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