CWPASADENA

I keep seeing the problem of fuel percolating being discussed on the CF.

Along with my C-2 Corvette, I also have Old Flathead Fords (I appologize in advance) which have the fuel pump up high on the back of the engine (where it should not be). In the "Old Days", these cars would occassionally have a problem of vapor lock in hot weather when the engine was working hard and everything was hot. With todays fuels with all the additives, this problem has become more pronounced.

I have seen published in one of the Ford Club publications where one solution to percolating or boiling fuel was to add a quart of Diesel Fuel to every 10 Gal of gas. The Diesel fuel will raise the vapor pressure of the Gas and help prevent this problem.

So far, I have not had this problem with my "Flatheads" or my '65 L79, but has anyone heard of this or tried it. A quart of Diesel per 10 Gal. of gas is not enough to hurt anything and may act as upper cylinder lubrication and is certainly easy to obtain and inexpensive.

Please let me know if anyone out there has had any experience with this.

This also may help the problem the F.I. Cars are having in hot weather with todays fuel.

Chris, CWPASADENA

Shurshot

That is a new one for me...... I would like to hear from someone about before and after plug readings as well as their performance observations.

It would certainly be nice if it delivers as hoped for without any other adverse reactions to the diesel fuel.

Maybe some of the fuel experts here will chime in

Doug

Frankie the Fink

I've never heard that one although I've seen it all over the decades; including using 10-12 old-time wooden clothes pins clipped to the steel fuel line coming into the carb (not much help but people thought it worked back in the day). Why dink around with fuel additives instead of some simple expedients like a heat spacer under the carb? It doesn't take much time and I made my own one morning out of phenolic.

kellsdad

I have no first hand knowledge on this topic, but a Google search offered the following. One, adding diesel fuel to gasoline will increase its resistance to vapor lock. Two, it's a very bad idea to add diesel fuel to the gasoline of modern engines because it can damage emission control devices such as the catalytic converter. Three, one web site also claimed that adding diesel fuel would dramatically lower the octane rating of the combined fuel.

Shurshot

That would be my biggest concern. I was not sure which way it would go since diesel motors work at such a high compression........ science was never my strong point

Doug

CWPASADENA

May be this would be OK for the old Flathead Fords. They are definately NOT modern engines. They do not have emission controls or Catalytic Converters. And they do not require much octane.

Chris, CWPASADENA

Shurshot

Back in the 80's a marina that I used to get fuel at for a skiff that had a new 6 cylinder outboard unfortunately had their gas tanks contaminated with diesel fuel. This was before fuel injected outboards and I had three carburetors that had to be completely torn down and rebuilt before the motor would run right.

Doug

Frankie the Fink

I get real leery of additives of any kind in most cases. Much better to try to help the engine components operate the were they are supposed to as closely as can be done with some of our modern constraints. E.g. Ethanol-laced gasoline.

Reducing the heat of the fuel along its path to the carb's jets is the route I chose..

Shurshot

Actually it is additives that are causing our problem and are why fuel percolates so much quicker today than it did twenty years ago.

In addition to that I do not buy all these "clean your engine while it runs" claims by the fuel companies. Twice I have torn down a low millage motor that had intake valves that looked like they had been dunked in tar and then baked.

I agree with you that the correct approach to the problem is to deliver fuel as cool as possible and into a carburetor that is also as cool as possible


Doug

MikeM

Vapor lock is when the fuel gets too hot in the fuel line prior to the fuel pump and turns to vapor. The fuel pump can't pump vapor and the carb runs out of fuel.

Fuel percolation is fuel boiling after it gets to the carburetor and turns to vapor.