Thanks for the posts I have seen so far.

The fuel filter is an inline type between the fuel pressure regulator and carb. It has 3/8 inch connections.

This car does not have a vented cap. The vent is a 1/4 inch tube that runs from the top of the filler neck and terminates inside the frame rail with about a 1/8 inch orfice in the end. I have removed the vent tube and checked to make sure it is open. Also drilled it out to the max opening possible with a 1/4 inch tube.

The pickup is located in the lowermost portion of the tank and I also run the tank full when at the track to make sure the pickup is never uncovered.

Since it seems to be temperature sensitive I am thinking it is vapor locking.

I am considering running the fuel line inside the car it get it away from any heat.

Thanks,