Barry - another guess (and it IS a guess) is that the old engines had a much lower compression ratio and therefore made less heat per unit of displacement. The fuel simply wasn't burned as efficiently. So now Tom has a pretty efficient engine in a bay made for a not very efficient engine and with appropriate air thru-flow for the old engine so there might be lots of compounded issues based on the old/newer engine situation.

Like I said - it's a guess.

Dan