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32 pontiac Six hesitation


TEDV
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I have hesitation when first pushing on accellerator. Engine pulls 17 lbs vacuum at any constant rpm and is eguiped with a Carter model BB-1D. Improves somewhat with choke partially pulled. There seems to be two settings for the accelerator pump by relocating the top attachment screw to one position or the other. This would change the length of stroke. Under what conditions should this be changed ? Other suggestions for cure appreciated, Thanks, Ted

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Hesitation from low RPM could be a number of things. The first I would check would be distributor advance.

The Carter BB1D is an excellent replacement carburetor, far superior to the Marvel that was used as original equipment. However, the BB1D has a couple of issues that must be addressed by the rebuilder.

The first is in the idle circuit. There is a jet which is hidden from view in the center of the lower casting that MUST be removed during the rebuilding process, so the area below the jet may be cleaned. Failure to remove this jet will result in idle issues. Idle issues can cause the symptoms you describe.

The second issue is the pump circuit. The BB1D utilizes a pair of "check valve cages" located in the bottom of the bowl as the inlet and discharge valves for the pump. These have a tendency to stick, if the carburetor is unused for long periods of time. These MUST be removed, cleaned, and checked for leakage during the rebuilding process. Failure to do so will result in failure of the accelerator pump.

The two settings you mention are for summer and winter. Use the shorter pump stroke in summer, and the longer pump stroke in winter.

Jon.

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  • 4 weeks later...

I run a BB1 on my 13 Buick. The mistake I made when installing a BB1 carb was the wrong gasket. Make sure there is a hole or slot in the gasket that aligns with the little hole in the top of the carb flange to connect it with the inside of the intake manifold.

Mark Shaw

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