Re: The Duchess Project: 1940 Super 8 Convertible Sedan

Posted by Joe Santana On 2021/1/2 10:50:04

PERCOLATING/BOILING FUEL: I think this article in HOT ROD has the answer.https://www.hotrod.com/articles/mixing-new-fuel-for-old-cars/

Highly volatile winter fuel blend and lack of heat insulation for the carburetor.

Here are some excerpts:

"There are two serious concerns with ethanol blends: too-high RVP (Reid Vapor Pressure) causing vapor lock behavior and percolation of the fuel. "

Here is exactly what I described:
"The problems begin with a vintage fuel system that employs a dead-head pump and float bowls where the fuel can heat up and percolate. This problem is particularly acute after running the engine for a sustained period of time at highway speeds, then suddenly coming into stop-and-go traffic. The associated heat sink effect will elevate the temperature of the carburetor and the fuel will boil in the bowl. This can lead to serious flooding on some cars and hard starting problems when hot in other vehicles, while many other cars may notice rough idle characteristics."

"To prevent the fuel from boiling in the carburetor or fuel lines you should insulate the carburetor base to prevent unwanted heat sink."

Fortunately I found in my misc fuel box some spacers and gaskets to do the job. In 2018 I modified a 1/2" wrench to get the mounting nuts. With the spacer I will probably need new carb mounting studs, but I'd have to get them out. I may. need to lose the throttle guard.

Won't. be sure if this solves the problem, but I'm going to give it a try.

Wish me luck.

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