Quadrajet Desperation

[rodney25]

Can anyone please help. Had a 1975 Quadrajet carb rebuilt for 1975 350 manual Corvette. The car starts idles and drives great. But if you nail the gas pedal the car hesitates and no pickup or power. If you cruse all is well and pick is perfect, problem is just when you floor the pedal is when it stutters with no pick up. No back fires just hesitates and no pickup. No vacuum leaks and new fuel filter. Should I give up and het the 650 CMF Holley replacement to the Quadrajet? Please help going nuts.

Thanks.

 

[John Mekisich]

Q Jet Desperation

Can anyone please help. Had a 1975 Quadrajet carb rebuilt for 1975 350 manual Corvette. The car starts idles and drives great. But if you nail the gas pedal the car hesitates and no pickup or power. If you cruse all is well and pick is perfect, problem is just when you floor the pedal is when it stutters with no pick up. No back fires just hesitates and no pickup. No vacuum leaks and new fuel filter. Should I give up and het the 650 CMF Holley replacement to the Quadrajet? Please help going nuts.

Thanks.

Q Jet will work well for your application when tuned correctly. Secondary operation is controlled mostly by the tension springs that hold the air valves closed. A significant bog as you describe can be caused by too little spring tension on the spring that holds the air valves closed. Your rebuilder should be able to easily make the required adjustment...........Q Jets sometimes get a bad rap as they are a sophisticated (for the time) misunderstood design that many times are not correctly tuned.

 

[Vettehead Mikey]

Agreed- a simple adjustment to the air valve. Make sure the accel. pump is working properly also.

 

[Hib Halverson]

Without road testing the car, my guesses would be either the recent rebuild was not done correctly and there is a problem with either the accelerator pump circuit or the power circuit or...as others have suggested, there is a problem with the secondary air valve adjustment.

 

[rodney25]

OK just saw that when the secondary flaps open they do not close back all the way because the Rod Sec Meters do not seat back down all the way. You have to play with it for it go all the way down and the secondary flags close all the way.
Will this cause the hesitation when the pedal is floored?


Thanks.

 

[Vettehead Mikey]

Absolutely. Tighten the spring till the door closes, plus another quarter or so.