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grey88gt · 02-27-2005, 11:54 PM

Well I agree with Rev . If the power valve is opening to soon, it will cause low mpg. Factory power valves normally open when vacuum drops to around 6.5 ". I always run power valves that opened up at 8.5 " and run a little smaller main jet. My old 400 in a 75 Cougar got 14-16 with a 8.5 " power valve # 61 jet and the car is very heavy 4000 + lbs. Anyway enough of my BS IAm outa ideas for ya again good luck!

02-27-2005, 11:54 PM	#7
grey88gt Registered Member Join Date: Feb 2004 Location: Skiatook, Oklahoma Posts: 193	Re: 8.5 mpg help Well I agree with Rev . If the power valve is opening to soon, it will cause low mpg. Factory power valves normally open when vacuum drops to around 6.5 ". I always run power valves that opened up at 8.5 " and run a little smaller main jet. My old 400 in a 75 Cougar got 14-16 with a 8.5 " power valve # 61 jet and the car is very heavy 4000 + lbs. Anyway enough of my BS IAm outa ideas for ya again good luck!