Carb question...

[intofx]

The Speed Demon 750cfm on my built 383 has never run well. I bought the "finished" car with 250 miles and now has 800 miles and now I'm faced with de-bugging it. I have the car at a shop now that has sorted a few issues. They replaced the oversized mechanical fuel pump with a smaller one, replaced the fuel filters before and after the pump, and added a spacer with an additional vacuum nipple to allow a port for the PVC. The car runs MUCH better now but at idle with the car hot, the fuel pressure drops to around 3 and tiny bubbles of fuel "jump" out of the vent at the front of the carb. The mechanic thinks the gas is percolating. I've been looking around and it seems that some people have had boiling gas issues as a result of block mounted fuel pumps or even gas lines being too close to the exhaust. The shop is looking at a heat shield for the carb but would that really do that much to drop temps enough to prevent boiling fuel? Any experience here or suggestions?

TIA,
Matt