I would double check timing curve. Too far advanced or retarded timing will cause overheating. I recently re-timed my Pontiac 350 in my GTO clone. Went from 38 to 32 degrees at 3,000. Engine temps dropped 20 degrees!!
What termostat, fan, and radiator are you using? Sounds like the engine is building heat at high speed. What is your cylinder overbore? .030" .060"??
chip
