The factory 261 piston has a compression height of 2.029" and .927" offset pin. How far down does the top of the piston set in the bore at TDC? How much can the block be decked "Safely"? I have 2 "848" heads that could be used on this engine to increase the compression without milling the head and dealing with valve train issues.

There are several pistons available in 3.875" bore, with a .9310" offset pin. The issue seems to be the compression height, most are around 1.58 to 1.68. Sil-O-lite has a AMC 2.5L piston (P/N: 3243HC) with a 3.875" bore, .9310" pin diameter, 1.592" compression height. This piston has a .116" deep "D" shaped head recess, it also has coated skirts and uses standard 3/16" and 5/64" rings.

Last edited by TUTS 59; 05/08/2024 1:33 PM.
~ Craig
1958 Viking 4400
"The Book of Thor"
Read the story in the DITY
1960 Chevrolet C10
"A Family Heirloom"
Follow the story in the DITY Gallery
'59 Apache 31, 327 V8 (0.030 over), Muncie M20 4 Speed, GM 10 Bolt Rear... long term project (30 years and counting)

If you don't like driving yourTruck, you won't drive yourTruck..| Living life in the SLOW lane