Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem
Idle problem
dlphil10:
Jets and rods won't affect my idle correct? The idle still runs pretty rough lIke a misfire. If I put my hand over the air horn primaries it smooths up. More fuel? Turn out that air bleed screw on top of the airhorn?
Cliff Ruggles:
If it smooths out when you cover the top some, it wants more idle fuel. Turn the bleed screw all the way in. Fine tune the mixture screws. If it still want more increase idle tube size and DCR's a small amount.....Cliff
dlphil10:
I had a chance to install the new 72 jets, new 42 rods, and new DA rods shipped from Cliff. The power difference is night and day, and the setup runs a lot more smoothly.
I replaced the idle tubes and I think it has helped some. The idle mixture screws are backed out around 3.5 -4 turns currently and the screw at the top of the air horn is seated all the way.
There still is a slight "Flub in the idle" and the off idle hesitation is barely there. It chokes down real quick and then picks back up quickly. I think it might still need more fuel, or vacuum advance tuned. The crane vacuum advance is in the second slot before being all the way locked out. I should also note that I have not drilled out the mixture screw openings, and I only have aorund 0.040" idle bypass. Should I follow the example in the book and drill the idle mixture screw holes out to 0.090"?
77cruiser:
Did you open up the DRC's any?
dlphil10:
No I have tried to avoid modifying things if I can help it but it seems that might be unavoidable. I never would have thought the 350 would be as demanding as it is, especially since the carb was made for a 428.
I didnt measure the DCRs because I didnt have anything to measure them that well. It should be a stock setup for the idle circuit, besides changing out the idle tubes and mixture screws.
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