I sent the information over to my dad, who has been in Pontiacs since the early 50's. This is what he came up with.
I found proof - the 1963 326 Pontiac engine was indeed 336 ci.
And '63 was the first year it was used in the Pontiac cars. My
Sealed Power catalog lists this:
326 Engine:
1963 Bore was 3 25/32" which is 3.781 and the stroke is 3.75, for
a displacement of 336.8 ci.
1964-67 - Bore was 3 23/32" which is 3.719, and the stroke is
3.75, for 325.89 ci.
We have been associated with Pontiacs for many years, and have
good reference material on them. The first year for the Pontiac
"326" engine in a Pontiac car was 1963. That engine was actually
336.8 cubes with a bore of 3.781 and stroke of 3.75.
The Pontiac "326" engine used from 1964 to 1967 (last year of use)
had a bore of 3.719 and stroke of 3.75 for a displacement of
325.89 ci.
We are not positive the 1963 336 ci was identical to the GMC 336
but believe it was. Many other parts other then block and pistons
would have been identical between the two engines.
If you need more help, let us know. Joe
