[Bob Parmenter]

Tom,

Vapor lock is usually more of a problem with mechanical fuel pumps mounted to the block, an electrical fuel pump, mounted remotely, is not very likely to heat soak. Also, one of the characteristics of reformulated gasoline is a lower vapor pressure to minimize HC emissions due to evaporation.

I'll go along with brother Putnam on the possibility of percolation since the Edelbrocks are an aluminum body, which is a good conductor of heat. The confusing thing is your comment about waiting 15 minutes for cool down. Percolation in the carbs SHOULD be more of a problem after shut down, when the coolant stops circulating and the engine heat soaks. Fuel flow, which has a cooling effect, also stops. It should take considerably longer than 15 minutes if it were percolation within the carbs.

One thing you didn't mention in your listing of fuel system components is a fuel pressure regulator. I'm wondering if, at lower speeds/lower fuel consumption, you aren't oversupplying the carbs and causing a bind in the float/needle components. With some percolation after stopping, the fuel level in the carbs drops to a point where they begin functioning "normally" again. It might be worth a call to Edelbrock's tech line to see if this is a possibility. They may have some other ideas as well and can give you some trouble shooting advice.

Good luck, this is a challenging one!