[jbon64]

i have a chevy 2 with a mid 70's 250. had the same problem , previous owner told me it had sat 3 years without running. when i drained the rad i noticed it had little flakes of rust that at times would plug up the drain in the radiator . i went to the extent of pulling the head off and power washing all the passages in both the block and head. after doing that my inline NEVER went over 180 degrees