442b

Posted back a few months ago about building my 1972 Olds Motor. It's a 1973-74 Toronado Block with G heads. If we shave the heads 30 thousands of an inch, will that change the compression ratio & how much? I believe from what I've read that the block being out of a 1973-74 Toronado, that the compression ratio is 8.5 to 1 which I know is not good. So, will shaving change compression & by how much? If you didn't guess, I'm not up on this stuff at all. Thanks for any help. Brian


P.S. I modified my original post. Engine Year. I thought it was a 1971 but it turns out to be possibly a 1973-74 Toronado Block.


Does anyone know how to tell what Engine Block I have?

64Rocket

Yes, it will change the compression. You need to know the CC's in the head.
It won't change that much. In order to figure it out, you need=
CC's in the head
CC's in the piston cup
Distance piston is down the hole
Thickness of the head gasket
Head gasket bore diameter
Get all the info, then you will know for sure.
Gene

442b

From what I've read about the heads I have, the CC's is 80. I don't know what that means but from what I've read, it seems to be good. I'm just wondering if I'm going to waste my time & money using these "G" Heads or should I search out a set of "C" or "F" heads?????????

Thanks for the help. Brian

dc2x4drvr

Milling .030 will result in about a 75cc chamber. To compute compression we need piston specs, head gasket thickness, and piston height at TDC. The G heads will work fine.

Run to Rund

If you mill the heads enough to matter, you will run into several other issues: you must mill the intake side the same amount, and then the intake bolts will be at the inner edge of the intake manifold holes (unless you take the milling amount off the manifold). Then the gap at the front and rear rails will be smaller, and you need to either mill the intake there or use RTV because the rubber seal is too thick. Taking off .025" will change compression somewhere around .3 that is from 9.1 to 9.4 more or less.

jaunty75

I hadn't actually heard that there was a connection between the two, but what do I know?

I'll have to try it some time!

442b

P.S. I modified my original post. Engine Year. I thought it was a 1971 but it turns out to be possibly a 1973-74 Toronado Block. The former owner had mill work done to the heads & added a mild cam, timing chain & gears. It's not quite enough for me, that's why we're doing more to it.


Does anyone know how to tell what Engine Block I have?

Also, I can pick up a set of "C" Heads off a 1968 442. Will these heads fit my block without major modification? Where can I get that info from? Thanks, Brian

64Rocket

If you think about it, shaving the heads to change the CC's in the combustion chamber is going to change the compression ratio.
Almost all the BB Olds heads are closer to 84 CC's, at least all the ones I have touch.
For me the '71/72 heads are better for an everyday driver for they have the factory induction harden valve seats for today's unleaded gas.
If you mill off .025 you should have no problems with the intake bolts lining up.
Your best bet is to mill the block, bringing the piston closer to the deck, will bring the most improvement. If you take .025 off the heads and .025 off the block, then yes you will have to mill the intake face on the heads. I never use the rubber ends seals anymore. A 1/4 inch bead of silicone, let set for 5 minutes and install the intake. It is best to make it a one time shot, for if you move the intake to much it screws up the silicone. I always use the aftermarket intake gasket. Even on the cast iron intake. I don't trust the tin valley pan.
If you get all the info I mentioned above, you can get a ratio you need.

Gene