I've had past problems with gas boiling in the carb. My carb was getting so hot it would burn you when touched. Solved it by blocking off the exhaust crossover port on the intake. I used 2"x3" pieces of tin cut from an old bathtub big block intake gasket. You don't have to remove the intake on your 383, just loosten all the bolts and slide the pieces in place and re-torque.