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Thread: Need help with Marine 4160 4BBL

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    Default Need help with Marine 4160 4BBL

    OK, I 'thought' it was better to replace my 30 year old QuadraJet with a new marine Holley, especially because on this engine (1988 OMC 4.3 V6) OMC and later Volvo switched from the QuadraJet to the marine 4160 part number 80492. This carb is supposedly calibrated for these V6 engines. I was able to get most of the OE parts needed for the conversion, like the carb adapter plate and the OE steel fuel line. I installed it and not matter what I did, it ran rich to the point of turning 2 sets of plugs black, had a surging idle and surged during acceleration. I tried asking techs for advice and did everything they suggested:
    Make sure that the idle transfer slot was not over-exposed. Carefully set the idle mixture (it would only idle acceptably with the mixture screws 1/2 turn out), with them the recommended 1 1/2 turns out it barely ran.
    Later on, I tried checking the floats, they were bit low and I adjusted them so they were level, same result. At this point there is no warranty on the carb (bought it new earlier this year) so in desperation, I pulled out the 30 year old QuadraJet, which I had rebuilt 2x before, with good results. I had heard they were tricky to rebuild but I did not find that to be the case at all. I just did a normal rebuild with a good cleaning and replacing all the gaskets, needle, seat, etc. Bolted it on and it ran, to my surprise, 100% better! Just like it did when I had previous rebuilds done by a shop.

    Here are the pix of the float, both were a bit low like this, and I just set them even as they are supposed to be.
    At this point I want the Holley to be usable in case I need it in the future, but I'd have to go beyond what I've done with setting it up and checking the floats. Thoughts on what else can cause this very rich running & surging?
    BTW, this carb is unusual in that there is no power valve. The primary jets (68) are richer to compensate. Also, turning in the idle mixture needles all the way will kill the engine.
    Never saw any fuel dripping from the boosters. I had some nozzle drip on my QuadraJet before I rebuilt it but the cleaning cured that.
    Last edited by Lou C; 09-15-2018 at 08:16 AM.

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