Quote:
Originally Posted by Jac Mac
I think you will find your problem is the power valve, its a bit lean for your particular engine combination- this is one part in a carb that should be checked/changed to suit each individual engine combo- in this case being lean means you have to go up on the number to cure it- lets say you have a 6.5 now ( ie starts to open @ 6.5" vac ) , try a 7.5 so that it opens a little bit sooner. Holleys were jetted about 5% rich in the 'good old' days to cover most situations, now things are a bit different in this PC world & if 'you' happen to have a good combo with strong vac signal it will hold the PV shut longer & cause a lean condition. This can be real pain in cruise mode & you find yourself constantly having to slow down /speed up to avoid the stumble.
Jac Mac
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Jac Mac - sorry to disagree with you, but the difference of gas getting to any engine with a 65 vs a 75 power valve is very small amount.
The numbers after the dash only determine at what level of manifold vacuum opens the power valve, and never has been an indication of the fuel flow amount.
There are two different "single stage" power valves.
The most common is the standard flow, and a 6.5 "Hg opening is part number 125-65
They also have a high flow unit and and a 6.5 "Hg opening is part number 125-
165
If you switched from a 125-65 to a 125-
165, then the power valve would open at the same vacuum level, but more flow would go thru the power enrichment circuit.
Before anyone changes the power valve open point (65, 75, 85, 105 etc) you MUST get a handle on the amount of vacuum at an idle, especially with a rude cam! And the vacuum gauge cannot be a cheap one that includes a ton of internal damping. With a cam with a lot of overlap, the vacuum could be going from 15 to 10 "Hg (for example). But a cheap gauge with a lot of damping would stay steady at 12.5"Hg. Therefore, you could install a power valve (10.5) that opens and closes at idle! Been there ... done that. I have a 4 inch diameter vacuum gauge that will follow the vac level of really wild cams.
Holley also builds a 2 stage power valve, but I'd avoid those.
To anyone having tuning problems on their Holley, go out and buy Dave Emanuel's book "Super Tuning and Modifying Holley Carburetors". After reading the book, start over and read it again.
http://www.holley.com/36-136.asp
http://www.buy.com/retail/product.as...01&dcaid=17902
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