Re: Vapor lock
I live in SW Florida and it's 85 plus a good part of the years. I had many
vapor lock problems with corn gas. On 100 degree days I had vapor lock
on 3 or 400 mile turn pike runs. At 65 or 70 MPH it ran good but if there
was road construction or an accident below 55 MPH VL started. Getting
back up to speed it went away. Also local driving, stopping for lunch for
1/2 the heat build up would cause VL. I did tests for several months under
the same conditions and determined after numerous "fixes" if the pump
was kept cool (fans and heat sinks) the problem went away. The problem
on the interstate proved that as long as a GOOD flow of cooler fuel from
the tank flowed through the pump it cooled it enough to prevent VL. I
installed a small fuel return line with a 'T" in the line right after the fuel
pump back into the filler pipe of the tank. There needs to be enough fuel
flow to the carb for high speed driving so you can't return to much. The
Stromberg carb has a fuel restriction hole in the float valve. It was
determined by Ford a .098 hole was ideal. A few thousandths larger
allowed fuel to push by the valve and a few thousandth less starved the
engine at high speed. This is described in the Ford Service Bulletins.
I found a restriction hole of about .100 allowed enough fuel return to cool
the pump and supplied enough fuel for at least speeds of 85 MPH. I don't
like electric pumps so this is my method. I also now run noncorn gas
because the alcohol attracts water, rusts the fuel tanks and eats the thin
brass float. This won't work on "A"s but defines the problem. G.M.
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