Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

OFF idle issue

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Jeffs68:
So here's the basic info.
Buick 7040244, converted to Pontiac primary linkage, Cliff supplied standard kit, with internals for a Pontiac 400 (stock, 16 heads, headers MSD ignition with an HEI)

Internal parts are:
42 Primary metering rods
Green power piston spring
69 Jets
Secondary rods DA
Float adjusted per Pontiac spec at 1/4 inch.

Starts and runs good, Idle mixture screws seem to be happy at 2 turns out.

Initial timing is at 13 degrees, about 36 all in.

When you cover the air horn with your hand to choke it OFF, it has very little to any RPM drop.

Also when you snap the throttle, it drops a few hundred RPMs lower than the set idle speed (almost to a stall) before returning to set idle.

When in gear and you initially give it throttle, it feels like it's loading up (gurgle sound from exhaust) with a slight hesitation, then it wants to take all you can give it, very smooth power delivery.

So, the APT screw is not installed due to the factory screw being completely wiped out (my fault)

I'm thinking, float adjustment? bigger primary metering rods to tame it down a bit?

Bowl plugs have been epoxied, no vacuum leaks, primary shaft bushed.

Ideas, criticism and snarky comments welcome  ;D

Cliff Ruggles:
Is the vacuum advance hook up?  Ported vacuum?  How much timing is it adding right off idle?.....Cliff

Jeffs68:
Yes, it's connected to manifold vacuum.

I'd have to check to see the actual advance OFF idle.

77cruiser:
Do ya think with the APT screw not in the rods are all the way down & it might be too lean?

Jeffs68:

--- Quote from: 77cruiser on July 31, 2016, 08:26:25 AM ---Do ya think with the APT screw not in the rods are all the way down & it might be too lean?

--- End quote ---

I suppose that's possible, I've never dealt with adjusting the APT before.

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