Holley Power Valve

[Jack M.]

Re: Holley Power Valve

Jerry,

I do NOT disagree that there may be some mention of 25R-591A-85AS as the Power Valve for the 3367 in some publications. The purpose of my reply was to assist the OP and contradict the statement made by the Allstate Rep:

"The other day I received a call from Allstate and the gentleman I spoke with was very nice and he politely explained to me that Holley has ALWAYS specified an 8.5" valve for this application."

I was showing indications where even Holley currently specifies the 125-65 Power Valve.

Please korrect me if I'm wrong, but the last Holley attachment you posted seems to contradict itself... and may have inkorrect info. For example, the RENEW (3-372) and MASTER KITS (85R-2676) for the 3367 and the 3370 (directly below the 3367) list the EXACT same kit numbers. What I find unusual is the individual parts are different (in your highlight)... the 3367 lists an 8.5 Power Valve, and the 3370 lists a 6.5 Power Valve. How can the exact same kits contain different parts? In addition, the 3370 carb is listed for a Corvette 327 engine... when it actually appeared on Corvette 427 engines.

Simple typos... who knows? Not an argument... just pointing out some things that make you go, hummm.

[Gerard F.]

Re: Holley Power Valve

Jack,

I did notice the difference in the 3370 which should be listed for a 427 and the power valves are different. Could be a typo, who knows.

There must have been a change in 66 or 67. In reviewing other 4160's for 65 and 66's on other pages, the 8.5 is predominantly specified. After 66 the 6.5 valves seems to be the standard. Perhaps they realized that the high performance cams with low vacuum at idle would not meet their 2 to 1 rule.

[William G.]

Re: Holley Power Valve

I've read all the replies to my original posting and want to thank everyone for taking the time to respond. I'll keep the 8.5" in case I ever blow the 6.5". Actually I have a fair selection of 6.5" power valves laying around and don't know which are bad and which are good. Suppose I need to invest in a mighty-vac so I can test them. As with many things relative to the old Corvettes, it would be interesting to determine why the change in specification to what would appear to be a simple fluid dynamics issue. [If there were some doubt in the minds of those responsible as to whether a 6.5 or 8.5 is best why did they not specify a 7.5"] It would appear that either would perform satisfactorily based on the profusion of sources listing either of the two values. Certainly there are more important things (even in Corvettes) to lose sleep over. Thanks again.

Bill

[Joe L.]

Re: Holley Power Valve

All------


I'll repeat myself: the only valve that GM ever specified (i.e. from 1966 or any later time) for the Holley List 3367 carburetor, also known as GM #3884505, was valve GM #3852470. That valve is a 6.5".

[William G.]

Re: Holley Power Valve

Thanks Joe....................I'm going to take that as gospel! Six-and-a-half it is!

Bill