carb flooding after shutdown!! help please

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May 17, 2008 | 08:23 PM

51merc

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From: medicine hat, ab

carb flooding after shutdown!! help please

Hi All...
Been a while...been working on other projects....a little bit here and there on the ol merc.
She runs great, but when i shut off the motor, i can hear gas burbling in the carb and it is comes out of the gasket between the carb and intake. What the heck is with that? Any advice would be much appreciated.
Also, what is the idle RPM on a stock 239 flathead supposed to be?
Thanks in advance...
Rick

May 17, 2008 | 09:26 PM

51ford fan

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Joined: Apr 2004

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From: Seattle WA.

I would suspect a faulty Needle and Seat or float adjustment. Or fuel pressure to high if your running an electric fuel pump.

May 17, 2008 | 09:31 PM

Old F1

Cargo Master

Joined: Feb 2008

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From: Windermere Valley,B.C. Ca

Hello Canuck neighbour, Sorry Rick, but it has been so long (good thing) since I worked on one of those I wouldn’t be any help. But I’ll give you my long distance wild a$$ cyber space guesses anyway.

If the float or needle and seat are allowing gas to leak past then it would try and fill up the manifold as long as the pump held some pressure. I defiantly don’t think it should leak out at the gasket because then when running it would suck air (vacuum leak), could it be leaking out the throttle shaft and not the gasket? If so carb is shot!

It is my understanding (probably wrong) that lead free gas as a much lower boiling or vaporizing point so maybe the percolating is just the gas boiling?

But I have been wrong before.

May 17, 2008 | 10:02 PM

fifty2f1

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Sounds like your float is sticking or needs adjustment.

May 18, 2008 | 10:47 AM

petey shoes

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idle rpm 675-750, enough to keep oil pressure up yet not pull truck when braking. thats my personal opinion/decision. i set engine up for (feel). these guys are right, float is the culprit unless using electric fuel pump, then it,s all about pressure

May 18, 2008 | 02:35 PM

51merc

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From: medicine hat, ab

yep..electric fuel pump

You guys mention float unless im using an electric fuel pump...which i am. Im using a 6 volt electric fuel pump, with a fuel regulator before the carb. (Actually running it through the mechanical, just removed the push rod to keep it stock appearing...).
Depending on how accurate the fuel pressure gauge is, im at approx. 3pds.
Im setting the float using the instructions that came with the rebuild kits. I have the chandler grove AA-1 carb..so am using the float level adjustment of 1-11/32" and the float drop adjustment at 1-7/16. At these settings, not much up or down movement in the float but it is at spec.
Any suggestions as to what the float should be at??
thanks again in advance..
Rick

May 18, 2008 | 04:24 PM

fifty2f1

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I am not familiar with your carb but if it has the same bowl setup as the holley or stromberg then I always set the float with the top off and it is more than a little bit, maybe 1/2" or so, I never really measured it. I don't see that it matters whether or not you have a electric or mechanical pump. Your 3# sounds just a bit high but I don't know for sure, I run mine around 2 to 2 1/2#.