41-48 vs. 49-54 pistons for 6 cylinder

[Jim Anselmo]

Can anyone tell me if there is a difference in the pistons for the 1941 -1948 239 6-cylinder versus the 1949 - 1954 pistons for the 239 6-cylinder? If so would you know what the difference is?

Thanks,

Jim

[poci1957]

The Pontiac parts catalog indicates 1941-51 are the same and early 1952 is too if they have a set screw pin retainer (later 1952 had a snap ring pin retainer). Then 1953 and 54 are listed with a different part number from those. The connecting rods apparently changed to reflect the new design too. Hope this helps, Todd C

[Jim Anselmo]

Thanks Todd!

[Bill Wilkerson]

The 'later' ('52-up) pistons can be used in '41 and later engines; the rods are the same. The later pistons are desirable and much stronger. They are aluminum

with 'full-floating'' pins vs. the earlier which are more prone to cracking / collapsing.

Edited December 4, 2012 by Bill Wilkerson (see edit history)

[Jim Anselmo]

Thanks for the info Bill. Sounds like thats what I should be looking for.

[PONTIAC1953]

if you are going to use aluminum pistons, make sure there is enough clearance, because pontiac straight eights and sixes with cast iron pistons could run with tighter clearances due to both block and pistons were both made from cast iron. aluminum pistons will expand at a faster rate. charles coker, 1953 pontiac tech advisor.