took my C heads off to fix things and since this engine is rebuilt,is the only way to check if it has the hardned valve seats to actually disassemble one valve?.not too much of a problem though.also which head gasket is the one to use.are there still steel gaskets or is composites universally used now?i have included a picture of the piston and would someone guess as to what compression this would be!.this is a '66 425 that has been rebuilt a while back in an 88.i took a break from this project but now i'm back on it.i'm also installing a 200r4 from my grand national in this thing.will read up on this in the apropriate forum.learning a lot here,thanks guys..

 

C heads did not typically come with hardened seats from the factory. Olds did not use hardened seats in production car motors until the 1971 model year. Some industrial motors designed to run on natural gas (which had no lead) may have used hardened seats prior to 1971. In any case, you will be unable to tell by looking at the heads anyway, since Olds used induction hardened seats, not separate press-in seats. The induction hardening simply heat treated the cast iron for a small depth, providing the same benefits as press-in seats. If the valves have ever been cut, any such hardening is long gone. If you are asking about aftermarket press-in seats, you'll have to inspect the heads.

By the way, the stamp on the block edge rail is not a factory marking so it was likely made by whoever rebuilt the motor.

 

you could measure that piston dish and calculate the cc volume and calculate the compression ratio.... almost done. Heads already off

 

thanks guys,and about the head gasket? i guess just a normal fel-pro gasket should do?..i don't mind if i lose a little comp..water injection will take of that.this is a street car that i will use as my "truck" for pulling stuff.thanks.

 

Your guess will probably be better than mine.
If the mating surfaces are good, I'd think that a standard gasket will work satisfactorily. Fel-Pro should work well.

 

Hey Ozzie you seem to very knowledgable and you provide accurate answers to the questions. But I must admit I have such a hard time reading your posts because of the font.

 

As others have mentioned, CC'ing the dish is the accurate way to go - but they look like standard low compression pistons.

 

I apologize for the font. It was an old lady with poor vision in my camera club that suggested it and I started using it for her and it soon got to be a habit everywhere. The size was used just to help out the "old timers" with diminished vision.

 

If you lose some compression then you will have less need for cooling the combustion chamber. You might find you can run on cheaper gas too.

Roger.