Quote:
Originally Posted by tom s
I'm sure the 64 GTO and the 421 HO used the same cam and we know the same heads so would assume had the same springs.Tom
|
Tom, this does NOT appear to have been true at the start of the year until EUN 190810, which would have been assembled some time around late Dec. '63.
Pontiac documentation exists which details the valve spring change for the GTO Head usage, no mention that it affected the 421HO Head usage.
If anybody wants, I can scan the document. It is also referred to in the '66 MPC for Valve Springs with the EUN break point noted.
b-man, would the '65 piston valve reliefs be same as '64? That 6 cc difference is a lot more than I would have guessed, but it seems to confirm that the cr was "controlled" by the valve relief difference between the 389 and 421.
But that still leaves the XX and XO stamp markings to be explained.