VCCA Home Forums TECHNICAL - 1945 AND NEWER 1949-1954 Vapor lock / Fuel boil - Vapor separator filter

I am looking for a solution to my vapor lock and fuel boil in my 1954 Chevy Bel air with a 3 speed.

The car runs great but starts to stutter a little when it is very hot after I have driven it for a long time. Hard to restart again after a long day of driving.

I am thinking about trying a Vapor separator fuel filter with 3 ports, the third port I believe would go back into the tank.

Has anyone tried this?
What filter did you use and did you run the return vapor line back to the tank with rubber fuel line? Or would it be possible to run it into a charcoal cannister?
I take it the filter would be attached after the fuel pump?

Thanks.

It is never easy to figure out exactly what is going on. A bunch of different heat related problems get aggregated under the term "vapor lock". I wish I had a good answer for you but I don't.

Those 3 port filters would NOT connect to a charcoal canister. They do go after the fuel pump. They send liquid fuel as well as vapor back to the tank via a return line. The third port on the filter has an orifice in it to restrict flow, so it just leaks a little fuel back to the tank in normal operation. There needs to be a return line, generally done in metal, back to the tank. This setup is to solve one very specific fuel issue, unfortunately not one of the most common ones.

The 3 most readily available filters historically are 1) the Chrysler k car filter, it is smaller than a normal inline filter, The third pipe has a bend in it, so it exit's parallel to the others. 2) Whatever Buick used in about 1963-64 on cars with 401 and A/C (I think). This probably has 2 of the 3 ports on one end, and is the same size as a standard inline filter. 3) The early 70s Chrysler filter, Like the Buick filter, this was also used with big engines and A/C. The third port probably exits at a right angle. I seriously doubt ANY of these filters are stocked in a typical parts store today, if they are even made anymore.

Has anyone tried it? Yes!, but on a Ford. It helped, but didn't really solve anything. I once had a 53 Belair with a 3 speed, and never had to resort to anything like this. It gets hot where I live, too.

I would start by figuring out if your heat riser works, and fix it if it doesn't. Make sure the centrifugal advance and the vacuum advance in your distributor work, and that your timing is set advanced enough. Retarded timing under any conditions will get your manifolds hotter than normal. I would have a good hard look at your cooling system. Is the engine running too hot?

Good luck, and I hope you find a solution.

My experience is that "vapor lock" is an indication of a failing fuel pump. Heat will always vaporize some of the fuel. A pump in good condition will pump enough fuel to overcome it. A failing pump will not. As for the hard restart when hot, that can be a number of things but linking the exhaust and intake manifolds so intimately together isn't one of Chevy's brightest achievements. Having said that, I was having that issue with my 38. A new ignition condenser ended up resolving the worst of the problem for me.

Thank you.
Everything is new in the cooling system and the temperature runs a little less then center on the gauge.

My heat riser is working. I have an electronic ignition and the vacuum advance works.

I will not try the 3 pronged fuel filter for now and investigate what you both speak of.

I may look into the fuel pump, it looks original....maybe it is starting to fail. I do not get any hesitation at highway speeds though.
I do have an electric fuel pump. Do you think that is worth trying?
Also insulating the fuel lines may help?

Be careful of the pressure of an electric. The mechanical pump is 5 psi.

I agree with Tiny that you need to be cautious with the electric fuel pump. The needle valve and float in the carburetor are designed to work with the mechanical fuel pump pressure which is typically 3 or so psi.

Some of our VCCA friends have a hidden toggle switch and only turn the electric pump on when starting the car.

If you do not know the history of the fuel pump you should consider rebuilding or replacing it as the next step.

I assume that you have an insulator piece between the intake manifold and the base of the carburetor. They do help reduce the heat transferred to the carburetor.

One other tip is to let the engine idle a couple minutes before you shut it off after a long drive that really gets everything heated up. The few times I have had hot start issues was after a 15 or 20 minutes drive at 55 or so and immediately shut it off. My fuel pump and battery are in good condition so I did get it started.

Vapor lock occurs in the fuel line BEFORE the fuel pump, Insulate about 4 feet of the gas line behind the pump.

I always thought it occurred after the pump. I learned something today.

Gene, can you recommend a specific insulation?

Make sure you avoid fuel with Ethanol as it will contribute especially if you live at any significant altitude.

You also need to make sure you are using summer gas. Over the winter months the chemistry of gas is altered to make it MORE volatile and vaporize easier. This will cause problems in warm weather. I have a backpack leaf blower that literally boils and spews fuel if I use winter gas in the warmer weather. Check with your area to see when they make the change from summer to winter fuel and back again,

Before making any changes to the system, try:

Starting a hot engine

As far as the electric fuel pump is concerned:

Electric fuel pumps and older engines

Jon.

After a drive on a hot day my car will stall/hesitate after being parked from a few minutes. It will start right up but after driving about a quarter mile it will almost quit. This has happened with both engines and two different carburetors.