Qjet idle rich.

[Hacksaw]

Originally Posted by john billups

GM 1980 305 w/ stocker cam, 2-3 inch vac.
I cant get a good idle, it loads up and it falling over about 90 ft. out then pickup a sec. later.
The carb was built by a local SS racer a few years ago. It has the pri. rods removed.
I have to have the throttle open a lot of turns to keep it running.
The fuel is being pulled from the mains and the idle screws have little affect.
I have tried other Q jet carbs, even a new Jet stage 3.
I guess the question is, how do I get this to run right.

Did this carb ever idle on your car? When you tried the other carbs did they work properly?

[Bob Mulry]

Did any carb ever idle on this engine??

Are the primary blades drilled??

2 or 3 inches of vacuum is nothing??

You might have engine problems and not carb problems..

Such as vacuum leaks, cam timing, damaged valves or too many to list..

Just sayin'

[john billups]

Carb worked on bracket 350. but w/ south a year later. Have rebuilt ,cleaned and blow it out. but has no
I have tried 3 other carbs on the 305.
problem on 3 different motors, all low vac motors.
smoked all the motors, no leaks, leak down good. plates drilled.
the motor will run with a Holley.
put a Jet 3 on this motor and still the same.

[kansas stocker]

Are you sure you have the right gasket between the carburetor and intake manifold?

[john billups]

I have looked at the gaskets but, I maybe should look at that . thanks

[HandOverFist]

Originally Posted by kansas stocker

Are you sure you have the right gasket between the carburetor and intake manifold?

Yes to this...there is a base gasket out there that is the mirror opposite of what is needed. Will cause a huge vacuum leak for sure.

[richie 2]

a huge vacum leak will cause it to be rich? I thought I would make it lean...

[HandOverFist]

Originally Posted by richie 2

a huge vacum leak will cause it to be rich? I thought I would make it lean...

Yes, lean in most cases. It would be hell to get any stable idle and would have to open the butterflies a huge amount just to keep it running. I finally put an O2 sensor on mine this year...no more guessing what it really wants.

[Hacksaw]

Originally Posted by richie 2

a huge vacum leak will cause it to be rich? I thought I would make it lean...

Just close off the choke area with your hand with the engine running at idle. Vary the amount of air that can enter the carb until it will run relatively smooth. If you restricted most of the incoming air, look for a vacuum leak or if it runs worse with any amount of air blockage, you are over rich. Don't test with a stone cold engine.

[Ed Wright]

Richie is correct. Vacuum leaks cause lean issues.
Throttle blades open too far allow fuel to be pulled from the boosters. Will cause very rich conditions. 1/4" float level should be fine. If you have not drilled the primary throttle blades, you likely have the idle speed screw run in too far, opening the throttle blades too far. Pull it, flip it over, the throttle blades should not be above the idle fuel slots in the base plate. Drilling air holes in the throttle blades is always needed with much of a cam, to prevent having to open the throttle blades far enough to pull fuel from the boosters.
Just look down in the primaries with it idling. Top of the throttle blades should be dry, with nothing coming out of the boosters.
Good luck.