piston id

[johnnyrod]

How do you tell if a piston is 9 to one 10 to one 8.5 to one. Mine look likw 9.5 s but is there suttle differances? John

[Dond409]

Do you have a picture of the piston in question? It gets kinda long to describe in words.

[tripowerguy]

If it is a cast piston and has no flycuts for the valves then you have a 90% chance it is a 9.5 piston. If it has valve relieves in the top it is probably 11 to 1. If it is forged it could be anything and you will have to take measurements with it in the block to determine compression.I know of no pistons that have numbers or any identifying marks to tell you anything about compression. :) Roy

[johnnyrod]

No fly cuts so I think they are the 9.5s. I thought that there might be a low comp. piston like in the 348 truck but i guess its all in the blocks comp relief. Does that make sense? John