Boiling Gas

[Papaciulo]

I have a '48 Roadmaster with a 320 cui. and a Dynaflow trans . I took it on a 60 mile ride and when I got to my destination , the car just shut off . I opened the hood and could see the fuel in the glass bowl was boiling . I waited a half hour and the car started , but I'm wondreng if anyone knows why this happened and any tips on how to prevent it from happening again .

[njlimbaugh]

You suffered the dreaded vapor lock. The underhood temperature was so high that the gas turned to vapor and the pump couldn't move up into the carb. I cured this on my 40 by installing an auxiliary fuel pump as low as possible on the frame between the stock fuel pump and the gas tank. You can install this in line with the stock pump. Either pump will not know that the other is installed. This puts the electric pump below the high-temp area and allows it to push fuel through the stock pump into the carb, vapor lock or not. Just install a switch on the electric pump so you can cut it in or out as needed.

[Pat n Pat]

Yes! the dreaded VAPOR LOCK! Unfortunately, modern fuel with ethanol vaporizes much more easily than the old High Test we had when the cars were built. I agree with njilbaugh; add an electric fuel pump.

Because electric fuel pumps push better than they suck, you should mount it toward the back of the car, as close to the tank as possible. We run a '41 Packard and a '56 T-Bird that we push very hard in cross-country rallies. We often compete in temperatures near 110 degrees, and over passes that are several thousand feet high; both of which promote vapor lock.

Our auxilliary electric fuel pumps are controlled by an under-dash switch. We have used it often to offset vapor lock. In addition, we turn the pump on when starting; gets gas to the bowl sooner.....a real plus with the 6 volt Packard.

You may also want to get some insulating wrap for the fuel line in the engine compartment. If you keep the fuel cool, you won't get vapor lock!

Many recommend a cut-out switch tied to the oil pressure sensor. A good idea if the fuel line breaks (in an accident). However, you lose the benefit of the electric fuel pump on starting. We don't use one, for that reason.....the electric fuel pump is not used all the time, only when needed!

Pat

[chub chub]

Is your heat riser flap on the exhaust manifold operating correctly? If it's stuck open it can cause that vapor lock too.

[stonecoldcars]

I installed a electric pump on mine as well as I made a heat shield at the base of the carb to deflect the heat from the exhaust manifold. I've driven the car in high temps with absolutely no problems.

[nali]

A wood spacer between carb and intake should help , no ?