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imnotmy77stang · 06-09-2008, 10:03 PM

a) even in the closed position there is *some* room for the secondaries to start to open (which they wouldnt because of the spring. hack when 67 said it relies on the signal from the motor you said it relies on the vacuum from the motor..... its the same thing.

b) you dont just up the power valve size. its not a size anyways, the number is at what vacuum it will close the valve. this way when there is a low vacuum condition (like when you stomp the gas from an idle and the vacuum dips low for a sec) the power valve springs open and gives the motor a shot of gas. at an idle, you want that power valve closed. now, i have head some people say use a PV with half the vacuum you have @ idle (say a stock holley 600 has a 6.5 they are figuring your motor will have 13 inches of vacuum @ idle). other people say to make it a little higher than that, like a 8.5 if you had 13 inches @ idle. me, right now i get about 10-11 @ idle and i've been playing with a 4.5 and 6.5

c) i noticed at some point in my tinkering that the short yellow spring wasnt stiff enough to make sure the secondaries stayed closed all the way even when the motor was off. this was causing random pain-in-the-ass-ness when trying to dial in the carb. i have a tall yellow in my 570 now IIRC, but even a purple would be ok since i shift @ 6800 when im being an asshole

06-09-2008, 10:03 PM	#8
imnotmy77stang 2nd Gear Member My Garage Join Date: Apr 2008 Location: Posts: 393	RE: carb??? a) even in the closed position there is some room for the secondaries to start to open (which they wouldnt because of the spring. hack when 67 said it relies on the signal from the motor you said it relies on the vacuum from the motor..... its the same thing. b) you dont just up the power valve size. its not a size anyways, the number is at what vacuum it will close the valve. this way when there is a low vacuum condition (like when you stomp the gas from an idle and the vacuum dips low for a sec) the power valve springs open and gives the motor a shot of gas. at an idle, you want that power valve closed. now, i have head some people say use a PV with half the vacuum you have @ idle (say a stock holley 600 has a 6.5 they are figuring your motor will have 13 inches of vacuum @ idle). other people say to make it a little higher than that, like a 8.5 if you had 13 inches @ idle. me, right now i get about 10-11 @ idle and i've been playing with a 4.5 and 6.5 c) i noticed at some point in my tinkering that the short yellow spring wasnt stiff enough to make sure the secondaries stayed closed all the way even when the motor was off. this was causing random pain-in-the-ass-ness when trying to dial in the carb. i have a tall yellow in my 570 now IIRC, but even a purple would be ok since i shift @ 6800 when im being an asshole __________________ wat?