I haven’t seen any service news for anything past 1955 nor have I seen any engineering features later than ’55.
Been searching since late last night and I haven’t found any reference to the change in any of the literature I have access to. The parts book –1957 just shows the 3836848 head as a replacement for 1953-1957. We’ve all heard how the 848 head is the head that you want to use and I seem to remember comments being made about the difference in this head to the earlier head. I’m sure there were other changes than the temperature port.
It appears the cam geometry was changed often which would account for the higher hp of the later engines but it only stands to reason if they were changing that then they would have also improved the porting.
DG


Denny G
Sandwich, IL