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Rev · 10-26-2003, 03:26 PM

The power valve stays shut with vacuum over that marked on the power valve. (usually 3-6 in. Hg vacuum). They work by using a small diphram that the vacuum works on to keep it closed. Only when vacuum falls below a specified amount does the power valve open due to spring pressure to admit extra fuel when the engine is under high load. If that little diaphram leaks, then the power valve stays open when it's not supposed to (at vacuum above the specified value). That makes the car run rich and not idle well and will give you black plugs. O'Reilly has Holley parts and a power valve is not expensive and is easy to install. I just did one a month ago.

Another thing that can make the car run rich and not idle well is the needle and seat valves in either prtimary or secondary float bowls. When the needle and seats are bad, you can actually see the gas dripping out of the booster ventouris at idle due to the too high gas level in the float bowls caused by the leaking needle and seats. They are also pretty easy to replace or sometimes even just flush out after removal.

My bet is that it's one of those problems. At least that's what it has been for me when the car all of a sudden runs too rich and won't idle well.

Rev

10-26-2003, 03:26 PM	#7
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	Bad power valve or bad needle and seat The power valve stays shut with vacuum over that marked on the power valve. (usually 3-6 in. Hg vacuum). They work by using a small diphram that the vacuum works on to keep it closed. Only when vacuum falls below a specified amount does the power valve open due to spring pressure to admit extra fuel when the engine is under high load. If that little diaphram leaks, then the power valve stays open when it's not supposed to (at vacuum above the specified value). That makes the car run rich and not idle well and will give you black plugs. O'Reilly has Holley parts and a power valve is not expensive and is easy to install. I just did one a month ago. Another thing that can make the car run rich and not idle well is the needle and seat valves in either prtimary or secondary float bowls. When the needle and seats are bad, you can actually see the gas dripping out of the booster ventouris at idle due to the too high gas level in the float bowls caused by the leaking needle and seats. They are also pretty easy to replace or sometimes even just flush out after removal. My bet is that it's one of those problems. At least that's what it has been for me when the car all of a sudden runs too rich and won't idle well. Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe Last edited by Rev; 10-26-2003 at 05:54 PM..