[Pete D]

I have a holley 6210 spreadbore, (650 CFM supposedly) for my set up. The combo is a 041 cammed, 1.65:1 crower rockered, performer RPM intake, 670 heads ported by Kaufmann's, stock HEI, eagle rods, forged TRWs, about 9.8:1 compression 428 with a wide ratio stick into a 3:55 posi.

The power valve is a 9" vac version. I have not tuned or otherwise adjusted anything on the carb. It has been rebuilt.

What are power valves for? What value of vac should it be set for? Jet suggestions?

One last question or two. What RPM would you think the engine's bottom end is good for? What is the cam's RPM range?

Many of the parts are in/on the motor as a direct result of reading posts on this board. I am _always_ open to suggestions by you gurus on the board.

Thanks guys!

[Pete D]

I have a holley 6210 spreadbore, (650 CFM supposedly) for my set up. The combo is a 041 cammed, 1.65:1 crower rockered, performer RPM intake, 670 heads ported by Kaufmann's, stock HEI, eagle rods, forged TRWs, about 9.8:1 compression 428 with a wide ratio stick into a 3:55 posi.

The power valve is a 9" vac version. I have not tuned or otherwise adjusted anything on the carb. It has been rebuilt.

What are power valves for? What value of vac should it be set for? Jet suggestions?

One last question or two. What RPM would you think the engine's bottom end is good for? What is the cam's RPM range?

Many of the parts are in/on the motor as a direct result of reading posts on this board. I am _always_ open to suggestions by you gurus on the board.

Thanks guys!

[TinInjun]

Pete:
The power valve on a Holley richens the mixture under full throttle, or at least thats what it should do.
I ran a similar combo as you, only it was in a 400. I could only pull about 10" of vac at idle, and I ran a 6.5 power valve in my Holley. I tried many different power valves till I found the one that didn't cause the engine to run too rich at part throttle. Just my .02 cents

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"Run wild with an Indian, not with the crowd in a Chevy"

[Skip Fix]

The power valve provides extra fuel beside whatthe jets flow at low vacuum when you acelerate. You want it closed so the number should be 1.5-2.0 LOWER than what the vacuum the motor pulls at idle so it will stay closed. Holley even made some two stage ones for emissions that open different amounts at different vacuum levels.

Some racers don't use them since the motor is at low vacuum when racing(also why secondary side often doesn't have one). And just jet accordingly. For a street motor this ususally will be too rich for part throttle driving.

They have to be played with a little to find what works good with your driving style. The also can blow out with a backfire and dump fuel irregularly at idle.

[SLOW 77]

Supposedly the rule of thumb to pick the correct powervalve is to take a vaccumm reading in gear at idle, then divide that number in half, then add 2 to it. This doesn't always work, the lower the car has in vaccumm say 10in then putting in a 7.5 will cause it to load up under part throttle, so there is a point were trial and error is needed. One of my cars that pulled 16" in gear I put in a 9.5 and didn't have any problems so it all depends, I drove with a vaccumm gauge to check though.