Hard starting when hot - vapor lock?

[Dustin Mustangs]

Thanks for all the feedback.

The fuel pressure is at 6.5 pounds as recommended by the engine builder. The regulator (Aeromotive) has a gage attached and the readings are consistent.

The electric fuel pump is two years old and also Aeromotive properly spec’ed for my set up. I have talked to the Aeromotive application engineers about my specific needs. I believe it is mounted correctly in the vertical position and on the frame below the tank. I do have a 100 micron filter between the tank and the pump where half the diameter of the filter is (barrel shape) geometrically below the pump pick up. Pump cavitation (the noise we are hearing) is a concern and this may be an element. The cavitation happens after full warm up on warm days, at low engine speed and usually in a turn – not a hard turn. You can hear it as it affects the regulator which is mounted on the firewall. I do not believe that the cavitation and the “vapor lock” (if that is what it is) are related.

I have checked the tank venting and could not detect any problems. Just to be sure I added a vent to the cap deep in the labyrinth above the gasket so as not to leak fuel. I think this can be checked off.

Fuel line is the 3/8 inch braided stainless.

Floats and carb has been inspected and tuned by a pro within a year. He believes that the problem is vapor lock as well. He theorizes that the Superformance fiberglass body is helping to insulate the heat (He wants to sell me an aluminum body).

Can’t tell you off hand what the vacuum is at idle, I have pretty bad vacuum at low engine speed – overlap I’m sure. In a hard stop with the clutch in the engine will normally stall for lack of vacuum.

I have not touched the carb settings since the pro work. The problem has existed from the beginning, before and after a number of professionals have worked on different parts of the drive train. None have worked specifically on this problem.

I’m going to guess Michigan fuel is not Oxygenated. Don’t know for sure.

The fuel log is just an Aeroquip set up with “T”s, see attachment.

I check and service both filters regularly, 100 micron before the pump and 10 micron before the carb. The problems existed before the filter installations.

Total timing is 34 degrees BTC. Don’t know off hand what the initial timing is. It was set by a very experienced professional about a year ago.