Compression ratio

[Ed51]

Could someone out there give me an idea what kind of C:R these pistons and heads will yield
The piston...

[Ed51]

And the heads...

[MK IISS]

Ed:

It's difficult to give you an answer with the information you have provided. The short block block appears to be a mid 70s or later "smog motor". It's not a SB 400 because theer are no steam holes. The heads look earlier and appeared to have been "milled". What casting # are they?

[Ed51]

I'm sorry,I was so busy trying to post the pictures that I forgot to say what it was.I was given this engine for nothing,guy was getting divorced and it had to go.The short block is supposed to be from an 80 Camaro 350 and the heads are 462 "camel humps" that have been extensively ported and those intake valves measure 2.050 across. The guy told me that it had a wild cam in it but he didn't remember whose cam it was or any of the duration or lift figures. He said it had no compression on # 8 ,so I opened it up to look inside and there is still cross hatch marks on the cylinders and NO ridge,bottom end looks real good.I looked at the heads closer and found a busted spring on the #8 exhaust valve,so that explains the loss of squeeze on #8. Makes me wonder WHY the spring broke,maybe it's that "wild cam".
I'm trying to guess the compression ratio so I can maybe get a new cam that is more streetable,I'm guessing it would be fairly high from the combustion chambers,as they look smallish,but the pistons are dished,so that is probably helpful.There are a lot of guys out here that are more hip to this stuff than I am ,so I am asking for there opinions. Thanks Ed :bow

[Southtowns27]

The combustion chambers do look small, but you do have dished pistons. I can't imagine it would be really high or anything. Probably in the 9-10 : 1 range if I had to just throw a number out there. See if someone can CC the heads and pistons for you, then you'll know for sure. Chances are someone put that wild cam in there but tried to run stock valve springs, hence the broken one.

[Kirby J]

well here you go the heads have 64 cc chambers . chances are they were milled about .005 that is typical for a machine shop . all that dose is to true up the surface of the head. looking at the picture you have 2.02 and 1.6 valves this is common as well . i would say the 80 modle 350 block had 9 to 1 compression with the stock heads. the 462 heads were for a 327 motor and when put on a 350 the compression goes up to 11 to 1 .. so with the dished pistons you are all over 10 to 1 comp. if your 462 heads have better than stock springs on them you will have no problem with the wild cam. the thing with the cam is you have to watch out for the vacume. when you run a high lift cam you lose the vacume at an idle and it will give you problems with your stock tranny and power brakes. unless you plan on running at the drag strip only you will need to put a smaller cam in for the street maybe a 268 duration . the 268 -274 duration cams are best for the street and work well with automatic trannys and power brakes. hope this helps. :cool:

[Fran Preve]

Even with those heads I'd guess 9.5, that's a BIG dish. 11 to one with flat tops maybe.

[Ed51]

Well considering the overpriced sh**ty gas they sell these days,thats probably a good thing. I have another question,how are valve diameters measured? When I put a micrometer over these intakes they measure 2.050 over the widest point. That is the corect method,isn't it?

[Kirby J]

you mesure the valves on the part that meets the head(the slanted part).. they mesure them at the top of the slant not at the bottom thats why you are getting 2.050..