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What would make Carb overflow when hot?

Old 09-01-2010, 12:54 PM
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Default What would make Carb overflow when hot?

Its an HP500 carb, we have already rebuilt it, set the float levels multiple times and it keeps doing same thing,
once you have been out running for a while and idle down to dock it will sputter and be way rich, as you look down carb bores you can actually see fuel trickling out of tubes. Makes it a scary propisition to dock.
When its cold it does not do this, idles perfect , nice 13.9-14.1 AFR , no fuel dripping.
Driving me bonkers..
Its sitting on a Ebrock Victor Jr with no heat passges so intake stays relatively cool.
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Old 09-01-2010, 01:36 PM
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Replace the needle and seat. If it is a brass float be sure it has no fluid inside.
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Old 09-01-2010, 06:44 PM
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How much fuel pressure when this happens?

Last edited by blue thunder; 09-01-2010 at 06:46 PM.
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Old 09-01-2010, 08:22 PM
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I had a Holley 800 do the same thing this spring. You could look down it and see gas pouring out. I just took the one bowl off cleaned it, set the level while the engine was running and never another issue.
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Old 09-01-2010, 09:00 PM
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Check the floats to make sure they are not filled with fuel.Also have you replaced the fuel pump with a higher volume. Those needle an seat cant take any more than 7 lbs .
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Old 09-02-2010, 07:58 PM
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not the vent tubes, it leaks out the venturi where fuel normally comes out when it is running.
Stock fuel pump.
Only does it after it warms up so if it is the float wouldnt it do it all the time?
Thanks!!
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Old 09-02-2010, 08:35 PM
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Bad Power valve? Idle not adjusted properly so that low idle vacuum lets the power valve open??
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Old 09-02-2010, 09:08 PM
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replaced power valve
good idle until it heats up and good vacuum.
Frustrating.
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Old 09-02-2010, 09:40 PM
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Try calling the Holley tech line
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Old 09-03-2010, 01:37 AM
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The only thing that will make fuel trickle out of the boost venturi at idle is the fuel level is too high in the fuel well. Why it only does it when warm is the mystery. Are the carb bowls properly vented?
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