power valve question

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Dec 26, 2005 | 01:34 PM

soccer794

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Racer

Joined: Jul 2004

Posts: 450

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From: Fredericksburg VA

power valve question

Tuning the carb today and I realized my power valve is rated for 6.5 in but I'm pulling 11 so I should be using a 9 in power valve correct? But the real question because I'm an aspiring engineer and want to know exactly why everything works is this...what effect does that have on the engine? Doesn't pull fuel in fast enough when the throttle is punched? Did switching to headers have any effect on my manifold vacuum? How much of an improvement can I expect?

Dec 26, 2005 | 02:37 PM

clem zahrobsky

Le Mans Master

Joined: Mar 1999

Posts: 6,744

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From: delmont pa

Cruise-In I Veteran

Cruise-In II Veteran

Quote:

Originally Posted by soccer794

the lower the number the later the PV is full open. if you use a PV with too low a number you will get a hesitation as you open up the throttle. that is why most SBC use a 6.5 PV and BBC use a 8.5 PV in the same carb because the BBC needs more fuel quicker than the SBC

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