Vapor Lock Fuel Choices

[Duke W.]

Re: Vapor Lock Fuel Choices

Duke,

Is this the thread you're thinking of?

https://www.forums.ncrs.org/showthre...84-fuel-system

Joe

That's one. Here are two more started by me.

https://www.forums.ncrs.org/showthre...nd-percolation

https://www.forums.ncrs.org/showthre...r-temperatures

The first thing to insulate is the fuel feed pipe in the engine comparment that goes to the fuel pump inlet.

BTW, the avgas minimum 40 percent boiling point is 75C, and the maximum 50 percent point is 105C. If you want to investigate further you can down load the ASTM D910 avgas spec from the Web.

Duke

[Michael G.]

Re: Vapor Lock Fuel Choices

The first thing to insulate is the fuel feed pipe in the engine comparment that goes to the fuel pump inlet.

Duke

I agree. I haven't messed with a 60 recently, but doesn't the fuel feed to the fuel pump go fairly close to the exhaust pipe? I'd warm the car up well and shoot that fuel line (& hose?) with an IR temp gun. I think you'll likely find it's above 160 degrees F. If the fuel gets heated that hot there, its only going to get hotter on its way to the fuel unit...

[Florian W.]

Re: Vapor Lock Fuel Choices

Mike,I'll check the temp there next time I have the car out. I'm kind of surprised that it would pick up much heat there. The steel hardline is outboard of the frame and away from the exhaust until it makes its bend in towards the pump. The line gets to within about 3 inches below the exhaust crossover pipe at its closest point. And by then, the hardline has transitioned to a rubber line which you wouldn't think would pick up heat as easily as the steel line.

[Michael G.]

Re: Vapor Lock Fuel Choices

After a few minutes of driving, it gets very hot down by those exhaust pipes. The 63 line doesn't get any closer to the exhaust manifold than 3" and my steel line used to achieve 170 degrees before the pump. If I recall correctly, insulating that line with reflective fiberglass tape reduced the fuel temp entering the fuel pump by 30 degrees or so.

Without trying to place blame on any particular chemical, my old chemistry degree tells me that 30 degrees makes a big difference in what boils off the hydrocarbon mix that is called gasoline. Maybe $10 worth of tape can save you a bunch of expensive gas. It can't hurt anything to try insulating the whole line, including the filter.