Technical power valves for 94

How are power valves marked as to size? I have several but have no way of knowing what size they are.

 

Most of the ones I've see are marked with numbers like 3.5 or 35, 4.5 or 45 and goes up from there. Can't recall the highest number. Number stands for inches of vacuum it opens. I have to take a magnifying glass to be able to read them. Number is stamped either on the side flats or on the rounded top of the valve. Hope this helps.

 

If you have a number of them laying around and they are used make sure that its not a leaker.

 

I use holley power valves with a lower value than the standard 7.5 even if it is for a single carb. Never more than a 6.5 and a 5.5 if having trouble with currently available fuels leaving plugs wet. Vintage Speed has them all but they may not be marked which worries me a bit. Check mine with a brake bleeder to sort them out but not very accurate. At least Vintage Speed will sell kits without the useless 7.5. When anything goes wrong they are tough to deal with. Good Luck: Fred A

 

All the ones I have are either new or ones I would be comfortable using. I have a dual setup using the 7.5 in the primary and 5.5 in the secondary. I get them from vintage speed but I cant find a number on them. Keep the suggestions and information coming, surely I am not the only one to ask this question.

 

If power valves are not numbered, it's hard to trust unless you're willing to trust them, which I don't when dealing with Vintage Speed who are notably unfriendly much of the time and drippy sweet if you catch them in the mood or ask the right question. Could have been a winner but blew it. Good Luck: Fred A

 

be careful on the newer powervalves they are manufactured differently and may require a thicker gasket to effect a seal in the bowl

 

Many of the replacements do not have the sharp 90* angle for the gasket face to the threads this makes the gasket ineffective. NAPA sells the PV's