Holley carb power valve questions

[Jeff H]

I'm rebuilding a Holley 4557 for my 70 L78 Camaro. It looks like it had a 10.5 primary and an 8.5 secondayr power valve. The rebuild kit looks like it has a pair 6.5 valves? Is that too low to go compared to stock? This carb is really old and has been sitting for years so I'm doing a cleaning and rebuild and can't compare before and after. I'm thinking I need to stick with someting closer to stock instead of the 6.5's that are in the kit.

[JoeG]

I'm running the same power valve numbers 10.5/pri--8.5/sec on a 3310 that I use on and off and the car responds real good and idles well with no surging--Bring your engine to operating temp and take a vac.reading and then step down 2 numbers....to start.

[Keith Tedford]

Our L72 engine came with 6.5 poweR valves front and back.

[VintageMusclecar]

Jeff;

The original power valves for a 4557 are 8.5's both front & rear. If your engine is stock, I'd stick to that.

Eric

[Jeff H]

The engine has 2" primary headers, HEI distributor, I think they're 1971 oval port heads(to lower compression), stock flat L78 intake and I'm going to assume stock cam. If I remember correctly, when I checked the compression and vacuum it was reading around 13 at idle. So I'm thinking the 6.5's will be too low. I would rather get the power valves right the first try so I'm in no hurry. Thanks guys.

[VintageMusclecar]

Jeff;

Check your PM's.

Eric