> M37 won't start when hot. I start it cold and it runs fine. Starts fine
> when cold. If I warm it up and try to restart it, it won't start. Wait
> until it cools down and it starts fine again.
Hi Bob,
My 1933 Plymouth (flathead six) has the same problem. Here's what I
think is happening, but it's only a theory at this point. The carb sits
atop a very large cast iron manifold. When the engine is running, the
fan airflow keeps the heat from the exhaust manifold from heating up the
intake manifold and carburetor, but when it is shut off, the manifold
heats the carburetor enough to boil the gasoline in the float bowl.
This in turn bounces the float up and down which raises the fuel level,
and floods the carburetor. I can get the Plymouth started only by
cranking for several seconds with the gas pedal held to the floor and
HELD THERE, since every time the pedal is depressed, the accelerator
pump puts more raw fuel in the carb throat. This is why I think the
problem is flooding.
I have not yet found a solution, but I have some ideas. First, there
should be a thick insulator between the carb and the manifold (5/8" on
the Plymouth). Second, I have heard that the Grose Jets advertised in
Hemmings and AACA magazine will cure this, but if you find something
simpler, I would love to hear about it. Oh another thing to check: be
sure that the heat riser valve in the manifold is intalled correctly,
moves freely, and actually closes the valve when the engine warms,
otherwise you are piping exhaust gas straight around the intake all the
time, not just when cold. Good luck!
Rob Root
1942 GPW, that starts good cold or hot
(1933 Plymouth)
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