I have a '78 Buick Q-jet on a '78 Chevy 350. I'd like to get it to perform better. I have a hell of a time trying to get it to idle properly as it wants to run at high rpms until I grab the linkage for the seconaries on the drivers side and pull foward...then it doesn't want to run.

On top of that the engine will run but will slowly decrease speed, then rev back up again. I've got some bacfiring thru the exaust. If I place my hand over the primaries the engines speed will increase some for a few minutes, then start to die until I take my hand off.

Driving it seems alright until you floor it and then it bogs.

:rolleyes: :confused: graemlins/angry.gif

I usually throw the quadrajets in the alluminum pile out back then bolt a Holley on.

do you have any vacuum leaks?
how are the idle mixture screws set?
what's the timing at? how is the vacuum advance hooked up- ported or manifold? what's the general condition of the engine?

any fool can just take the carb off and throw on the "belly button carb" (the Holley- everybody has one. get it?) but maybe- just MAYBE- the carb needs to be rebuilt or there is some other problem causing it to run crappy, and a holly will mask that by being calibrated richer.

I would throw out the Q-jet but right now it has to work for me.

There are no vacuum leaks that I'm aware of. I can't say where the timing is set to cuz I can't even find the mark on the balancer when I aim the gun at the tab. The screws....well they were (I'm guessing) 1/2 the way out. I tried turning them in a few times but no luck. The vacuum advance is hooked up to manifold vacuum. As far as I know the engine itself is in good shape.

http://www.geocities.com/gtopercy/Pictures/quadrajetTech.html

http://www.corvettefaq.com/redir.asp?site=215

Start with the 2nd link - you may have to click on the underlined "HERE" in red.

Is there a lot of slop in the primary throttle shafts? If so, it needs to be rebushed before it will ever run good.

My Qj's have generally run as good or better than my Holley, with the additional advantage of 1-2 mpg better fuel economy.

I'd be really reluctant to start throwing too many stones at the Qj if you aren't sure where your timing is set, and if you haven't set the idle a/f mixture with a vacuum gauge.

Best bet is to check for leaks in the primary throttle shafts, get your timing nailed down, and adjust the idle mixture using a vacuum gauge/tachometer.

Mike