| flathead48 | -- 05-30-2010 @ 10:19 AM |
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Correct power valve for a 48, I keep thinking 5.5 but not sure??? Thanks
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| supereal | -- 05-31-2010 @ 8:56 AM |
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That should be OK. The number indicates the vacuum level (hg), or lower, where the valve opens under heavy load conditions. Most power valves are OK, and often better than the ones in the kits. Problems have been noted with the repros, particularly with the seating rim, and with the gaskets in the kits. If the valve leaks around the diaphragm, it has either been attacked by the "new" gas, or ruptured by a backfire. If you are unsure of the rating for your engine, attach a vacuum gauge. The opening of the power valve should be about 2 inches (hg) below the lowest steady-speed engine vacuum observed.
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| tbirdhandyman | -- 05-31-2010 @ 7:12 PM |
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Supereal: Could you please provide a part number and your source for the replacement power valves? I tried to find one without buying the complete kit for my Holley 91-99. I finally ordered two from a speed shop. Holley performance part #125-85, and when I got them, the brass part was too big to go up into my carburator. I had ordered the 8.5 because that was what two of my units had in them. Being special order, I had to eat $38.00. That's life! Tbirdhandyman
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| TomO | -- 06-01-2010 @ 7:44 AM |
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Vintage Speed is a good source for power valves. If your 40 engine is stock, a 6.5 valve will work fine. Ask for the valve that is machined to work in the 91-99 carburetor. http://www.parts123.com/parts123/yb.dll?parta~partsort Speedway Motors also sells power valves. Tom
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| supereal | -- 06-01-2010 @ 8:13 AM |
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Robert: We bought an assortment of power valves a long time ago, and I can't recall the source. TomO gave you a good lead. All carb kits usually contain a replacement valve, and the kits for the 38-56 carbs sell for under $25 at C&G. Lots of owners seem to worry about the things, but I've subbed them with above and below the "correct" rating with little, if any, difference. If a car is running well on the old valve, we usually just replace the gasket and leave it in. If we install a kit, we give the owner the extra parts "just in case". A good many kits contain inferior parts today. Often a $5 gasket kit is as good, and better, than a rebuild kit with poor parts.
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