Whats my (ball park) compression ratio?

[HAFROD]

I built a standard bore 350. Its never been decked. I put in stock rods with cast flat top pistons with 4 valve reliefs. I have stock unshaved 882 heads 76cc. I used the Felpro steel head gasket shims with copper coat sprayed on for my head gaskets. I think they are .015 thick. I'm curious as to what grade of fuel I need to run.

 

[drogg1]

Guessing a few things and using this calculatior:

https://www.uempistons.com/index.ph...e=comp&zenid=67188368198500ff0d49c996bb380449

I'd say it will be around 9.5:1 static. With a decent size cam, you should probably be fine running regular although premium would be good to be safe.

 

[lilbowtie]

Not a fan of the thin head gasket especially not decking the block & resurfacing the heads. Check your valve train geometry.

 

[Mike P]

The big question is the what the deck height of the pistons is. As far as the heads go, from CCing a bunch of factory iron heads, virtually all of them are larger than advertised. Assuming the pistons are just the standard rebuilder type I suspect that your real static compression ration is around 8.5:1.....even with the shim type gasket. Depending on the altitude you're at you might be able to get by with regular and worst case mid grade.

Unless it pings and hammers when you start driving it I'd start out with mid grade for the first couple of thousand miles (until everything is broken in good) then do some fine tuning and play around with a couple of tanks of different grades and see what the car likes.

 

[HAFROD]

I checked my roller rocker tips on the valve stem with a Sharpie mark and rolling the engine over two revolutions. It is a little off center but barely.