does anyone know the compression ratio of this year 455?

is it worth buying?

and i just found out my 350 isnt worth rebuilding the crank has to many deep grooves and a lot of thrust play and it needs a sleeve.

 

About 8.5:1. 1971 was the first year of reduced compression ratios to accommodate low-lead gas. The good news is that the G heads will have induction hardened valve seats.

The last 455 Olds block was cast in 1976. ANY 455 is worth buying.

 

can the compression be steped up on a 71 or newer engine by simply changing the heads and pistons?

 

Changing to the pistons without dishes will increase your compression. Summit's rebuild kit offers the pistons with reliefs that will be higher compression than any smogger engine. They are cast, but they aren't 8.5:1

 

All Olds big block heads have the same 80-ish CC chambers (except for the 68-69 D heads that have a designed chamber of 72 CC). Note that as-cast the chambers tend to run about 83-84 CC. The compression ratio is varied by changing the size of the dish in the pistons. The factory low-compression pistons look like soup bowls.

 

so with some nice flat top pistons what compression ratio would you think i would be close to?

 

To accurately calculate the static compression ratio of any engine, the following values must be known:
Bore diameter, stroke length, rod length, deck height, combustion chamber volume, cylinder head gasket compressed thickness, and cylinder head gasket bore diameter.

http://www.rbracing-rsr.com/compstaticcalc.html

 

These are the pistons out of my 400. I've never seen flat tops on an Olds until these. I was told these are the stock pistons. 400olds008.jpg

 

W-31s also used flat top pistons from the factory.

 

You need to watch whose advice you are listening to.

No way to guess without knowing the piston specs, compression (pin) height in particular.

The internet is full of bogus information. You need to pay more attention to where you get your information.

Try it with the specs from your own engine.

Norm