Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

Fuel pressure?

Re: Qjet idle rich.
 

Fuel pressure
Started at 7psi I how have it set at 3.5psi.
Float is at 1/4 " , have changed float and needle & seat.

Re: Qjet idle rich.
 

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

Re: Qjet idle rich.
 

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'

Re: Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

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

Re: Qjet idle rich.
 

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

Re: Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

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

Re: Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

Bingo... I have Idle... found a plug may of come out of the choke vac. port. I also changed the gasket between the body and base. The thing is the carb worked well for 3 season's then went bad, so I was hopping it was a small thing and it was. thanks to all with you input. Often it the thing right in front of your face.

Re: Qjet idle rich.
 

This is one of the reasons this forum is so valuable. Racers helping fellow racers, and a thousand years combined experience. In some ways the Internet has been a pain for society, but when it's used for good, it's awesome. Glad you found your problem.

Re: Qjet idle rich.
 

x2 :)

Re: Qjet idle rich.
 

now my fresh rebuild is rich...I mean way rich. only thing I didn't do was to repair the well plugs. im swapping in a gm distributor too as I believe our import unit might not even be providing enough spark to fire the mixture...the carb might be just fine...

Re: Qjet idle rich.
 

With the primary rods removed you must block off the plunger well and reduce main jets, to like a pair of 66's. When the well plugs seep it has little effect when the engine is running. It's when it sits, it will drain the fuel bowl.

Re: Qjet idle rich.
 

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.

Re: Qjet idle rich.
 

Also ensure the secondary blades are fully closed and the hanger allows the secondary rods to seat down in the taper. Many times when a carb is converted to "non-progressive" secondary opening, if the linkage isnt just right, the secondaries will stay cracked open, and just pull the air valve open a bit at idle, lifting the secondary rods out of the tapered seat section and it will pull fuel from the secondary tubes and be crazy rich.