Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor

Float and APT setting recommendations

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T/A_455:
And last update for the night...  Sorry for the running dialogue here - I just figure it's better to provide too much info, rather than not enough.

After observing fuel in the secondaries at idle, I took a closer look around the airhorn and realized that the gasket was saturated.  So I popped the top and dropped the float down to 13/32".

Idle is now noticeably smoother.  To the point where I think I can attribute any fluctuation to the cam.  Vacuum on the gauge is also now relatively smooth - bouncing within a half inch range, versus a couple of inches, much more violently, before.

I adjusted the idle to max vacuum (about 14 in) and set it at 750 rpm and went for a test drive.  Part throttle still has a stumble, but it seems more consistent and softer now, if that makes sense.  I suspect this may be correctable with further APT adjustments?  One other observation - I set the idle at 750 rpm with the engine warned up, went for a drive - during and afterwards it would idle much closer to 1000 rpm.  I am interested to see what it does when I start it up cold tomorrow...

Ethan1:
 Stock float height for that carb was 17/32" from the factory.

Marx3:
what happens if you cover the secondary air flaps with a cloth ? If this affects idle, you are propably sucking air past the secondary plates and need to center them. 

It sounds like you need to go for testdrive and fine tune the APT. If you have it at 3 turns up form seated, you can try raising it 1/2 a turn, go for cruise. Go at it 1/2 turn at the time.
I'm no expert, but your jetting sounds pretty good for your engine. 
I dont know the stock MAB size for that carb number, but as far as I know, only chevy units from that time, had the large MABS.

Cliff Ruggles:
Have you checked fuel pressure during any of this? 

That carb should be fine at 9/32" float height.  Seeing an improvement with a much lower float setting indicates high fuel pressure.....Cliff

T/A_455:
Thank you all for the responses.

Cliff: No, I have not checked it yet.  I will do that next.  I assumed that I was safe there from the pump specs, but I do know what happens when you assume...

If pressure proves to be too high (more than 8psi? 7.5psi?), do you think a pressure regulator would be the solution?  Or would an adjustment to the needle/seat size be workable?  (Please forgive my ignorance if this is an obvious question.)

I'm afraid I don't have the current seat size handy - I did replace it as part of the kit I received from you though.

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