Vacuum signal

[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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