Hot Rods Jahns 265 Chevy Domed Pistons

Does anyone know what the dome CC is on these Jahns pistons? I am going to be using these in a 1955 265 engine and am trying to figure out what my compression would be.

 

That is covered here:
https://auto.jepistons.com/blog/how-to-calculate-engine-compression-ratio-and-displacement

 

Thanks for the link, I'll read that over.

I guess it would help if I uploaded the pictures of my pistons. Here they are.

 

Cover piston top with a light coating of grease. Lap 3-4 layers around the piston with 2-3” masking tape. Fill with plaster-of-paris. Remove. Measure hole. I bought a plastic barrette on line for a few bucks and now do every cylinder head and piston top.
What you don’t know can hurt you. … . Boy. Those are some old castings.

 

Looks like some hefty compression if you're using stock heads.

 

From the side, they look very similar to a set of Z28 302" pistons I had, that had the higher
12 to 1 compression ratio. (Not the 11:0 to 1 pistons.) And Z28 pistons are slightly longer from the first ring to the
edge of the piston dome.

 

Consider the size of the engine and you'll understand why they look so huge.

 

It takes a lot to get over 10:1.

 

Ring spacing looks W-I-D-E; smaller dia. at oil ring up?

 

Those are really cool, finding a set with box.... winner...

 

It would seem that the company continues on in some fashion: https://powersports.jepistons.com/our-history

It could be worth giving them a call.

 

Heavy pistons...
I had a set for my .06 over, 409, years back. They musta weighed 10# each !

Oh and DON'T go by the Jahns, "piston to wall" clearance spec. It's for race engines, and probably on nitro.
Better to go a coupla thousandths (or more !) tighter. Ask me how I know. a whole story's worth.
Mike