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Thread: Off Idle Bog

  1. #1

    Default Off Idle Bog

    Hi, I recently got a car with a Holley carburetor on it, and first of all I can't find it listed anywhere. The numbers on the front are 80453 and below that it is 3345. All that I could find was that it was a 600 cfm carb. Other than that, it bogs off of idle. I've set the accelerator pump in every place from the tightest to the loosest, and tried all the cam settings on the one I have, and both the primary & secondary float levels are at a good level. All I can think of is going up in nozzle size because I have 31s right now, and it's on a Ford 302 engine. I was hoping to avoid that, so any other ideas?
    Last edited by TheJugulator; 05-10-2017 at 11:06 PM.

  2. #2


    You have '31s' in it? Are you talking about the jets? Off-idle flat spot/bog is one symptom of insufficient fuel to support the amount of air you're letting in with the throttle. There is a theory that I proved wrong many years ago, that says to use smaller jets and a bigger power valve. The belief was that the power valve coming in earlier would compensate for the smaller jets on acceleration, so you wouldn't have a flat spot and you would have more fuel economy cruising on the lean mixture. I believed the guy who told me that and fought it for over a year before finally going back to the 55 power valve and 70 jets. This was on a 500 2V on a Ford 260 Mustang many years ago. Finally got it running right with nice dark gray exhaust pipes right before I sold the car. Wouldn't mind having that one back - it was a '64 1/2 convertible with the 260 & generator.
    Anyway, seems like you should have something like 65 or 70 jets on your mains, and maybe 65s on the secondaries on a 302, depending on what else might be in the engine (cam, heads, dual exhaust, etc).
    You might also have the wrong power valve in it, assuming there are no air leaks or clogged passages. That's the great thing about the Holley modular system - if the metering block is bad and you can't fix it, get a new one. Find out what power valve is correct and make sure you have that in there - probably get a new one anyway since they can go bad. Then you can put everything back like it was or kind of in the center of the adjustment range and see how it goes.
    Is this with automatic transmission? Do you have vacuum secondaries?

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