I disagree on SPAL being a problem. It's all we run, and they push more air than others I have had. The Rep for PRC radiators told me they have tested every fan companies send to them for evaluation, and SPAL comes out tops every time.

How hot is your car getting? You certainly have all the good components from radiator on down. You say you have your vacuum in the manifold........it should be on the ported side of the carb (not full time vacuum) How is your timing?

Does it drop when you start moving?

Don