The Ford Barn

Tom Endy · 01-10-2016, 04:35 PM

The GAV controls the amount of fuel that reaches the cap jet in addition to what it receives from the comp jet. The comp jet is much smaller that the cap jet. If the GAV is closed the only fuel reaching the cap jet is through the comp jet. When you open the GAV it ports fuel around the comp jet and the cap jet receives much more fuel.

For everything to work correctly each jet in the carburetor should be flow tested to be sure they are within the deign spec. Most reproduction jets are wide of the mark.

My car runs best with the GAV open about a half a turn. More than that and it will run rich. As long as you can control how your car runs with the GAV it is probably ok. Your comp jet may be on the large size.

Tom Endy

01-10-2016, 04:35 PM	#2
Tom Endy Senior Member Join Date: May 2010 Location: Southern California Posts: 3,168	Re: Why does engine run best with GAV almost closed The GAV controls the amount of fuel that reaches the cap jet in addition to what it receives from the comp jet. The comp jet is much smaller that the cap jet. If the GAV is closed the only fuel reaching the cap jet is through the comp jet. When you open the GAV it ports fuel around the comp jet and the cap jet receives much more fuel. For everything to work correctly each jet in the carburetor should be flow tested to be sure they are within the deign spec. Most reproduction jets are wide of the mark. My car runs best with the GAV open about a half a turn. More than that and it will run rich. As long as you can control how your car runs with the GAV it is probably ok. Your comp jet may be on the large size. Tom Endy