Supercharged flathead floods on startup.

Why does our engine flood.We have a new 39 merc 276 Cu. motor isky max 1 cam two rebuilt 94 holley carbs with a supercharger on top.It has 14.5 inches of vac*** at idle , 2.5 psi fuel pressure at 1500rpm 3.5 psi with motor off , electric pump. It will start from cold with no choke or throttle then most likely immediately flood and be hard to start. In other words run breifly a few cycles and seemingly flood.Have changed to late model holley 5.5 power valves. The originals had a leaking problem.The valves clear the float chamber body ok. Where else do we look.

 

Late model power valves usually don't have the correct seat & raw fuel will drain right past them. They are easiliy machined for the correct seat.

Otherwise, what type of supercharger and what's the drive ratio?

 

im going to agree with flat ernie on this one.. its prolly the new power valves.

 

Have checked power valves on the bench and appear to seal Ok no visible wetness.
This is the same Scot supercharger I ran 12 years ago, I just freshend it up. We did have a problem with the original carb rebuild kit Power valves ,in that they did leak ,one was definately ruptured and the other I think was too. Raw fuel was running out the throttle shafts etc. But now that seems to be cured. New throttle shafts were installed during rebuild.

 

what ernie says, late power valves dont fit properly and will leak. try 2 washers on them and see if that makes any difference as a test.

 

To validate - put carbs on bench, fill with fuel, let sit. Come back in 10 minutes - if fuel under, PVs ain't seating.

"Look" like they're seating ain't necessarily the same as seating.

FWIW - I've yet to see an unmodified late-model PV seat correctly.

 

Tried them on the bench yesterday and no apparent leaks. Two washers may cover the outlets. I Just used some loc***e sealer around the washer.

 

94's usually leak at 3.5 psi, try less pressure. What brand of regulator are you using?

 

check the needles & seats . turn the electric pump on & look down the carbs ,

 

Use a Malp***i Filter King , Best regulator bar none , run 2-2.5 psi.

 

do the power valve bench test with the throttle body removed, set the gas filled float bowl center section on a folded paper towel, leave for a while, if it is leaking you will see a yellow spot on the towel. could it be your float setting is too high? or a float with a pin hole? test the float by heating it with a wooden match, if it has any gas in it, steam will come out of the pinhole. test the needle & seat, try to blow thru it while inverted.
it sounds like you know what you are doing, so i'm sure you will get-r-done. these simple carbs can drive you nuts. I love those flatties.
jdl