Pistons

[whitehillbilly64]

Good Morning.
I am stripping a 53 motor for my 53 80 inch.
I was wondering if anyone recognised the Numbers on the Pistons?
From basic measurements I took from the top of the Cylinder, I believe they are 30 thou oversize?
Brass plate on Block.
Thanks.

whitehillbilly

[whitehillbilly64]

Numbers.

[Blknight.aus]

Best guess.

H and X might represent nominal oversize letter and then the tolerance.

Some pistons were made to a nominal size (10 under, standard, 10, 20, 30, 40, 50, 60 over) and then had a tolerance of 2 under, standard, 2 4 6 8 over and that also had a letter x or z no marking, a b c d respectively.

IF a manufacturer swaped the norma. -.010 (no marking), .010, .020 etc with a letter code I could see it the letters decoding as the oversize and tolerance, with the next 4 being a batching number and the final number being stamped into the piston during asssembly indicating that its the #4 piston. in that engine.

Alternatively the 4 digits might also be the same as the last 4 digits of the engine block number.

[whitehillbilly64]

Thanks for the reply.
All 4 pistons are stamped the same, except for Cylinder number.
My other 53 motor has graded pistons fitted, so on a very worn STD bore.

whitehillbilly