I just want to know if any one has done this or if it is even possilbe?

 

Yes you can mill down the deck surface of a cylinder head to reduce the size of the combustion chamber. 58cc to 56cc's won't take
much, maybe .015". Generally you can flat-mill these heads down to the valve seats.
About .060". Angle milling will get you more.
Make sure your replacemant head gasket is the same thickness as your old one or you may actually drop net compression ratio.
Or account for the difference when you shave the heads. You may have to machine the intake face of the head to restore alignment of the intake manifold after shaving the heads.
I'd advice against raising the actual measured compression ratio above 10.0:1
as it will require you use higher octane racing fuel to avoid knock. Figure on a 4% increase in horsepower and torque for every whole number increase in compression ratio.
It will make more torque and be more responsive too. But requires the use of higher octane gas.

 

Why not just use thinner head gaskets if you want a compression bump? Or, if you've had this done and are wondering about clearance, thicker head gaskets.

 

Factory stock motors usually come with a very thin .015" shim head gasket. Most of the replacement ones (felpro) are thicker .038" to .042" If you shaved the head
say .015" to reduce 2cc's and reinstall it with a common replacemant .041" gasket, you would actually loose compression ratio.
Engineer eh.....

 

I just had mine milled .030" and I plan to use the felpro gaskets that compress to about .038"
FBIRD you are right on again. I'm shooting for about 10:1 compression.



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1986 Iroc 305 small block chevy getting modded now for speed

 

Interesting, most of the engines I've worked with had .039 or .040 compressed height head gaskets to begin with. That's why I suggested thinning down to .020 or thickening to .060 to lose or gain about a half point. I prefer not to mill the deck or heads, I like to order the master kit with pistons to adjust the compression ratio to wherever I need.

 

fbird88 was right. my 305 had a very thin metal shim about .015" or close to it. i can see losing a lot of compression if you go with felpro gaskets and you dont mill the heads down.



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1986 Iroc 305 small block chevy getting modded now for speed

 

Did my homework, most stock engines do use .015-.020 shim. (Most engines I've worked with have been components when I started with them, so knowing that most gaskets come .039 to .04 thick I assumed that was the norm.) I do know that every .020 of gasket equals 1/2 point of compression, and that each 1/2 point of compression is worth 5-10HP on average.

 

Each point of compression will give you about one hp per cylinder. You have to be desperate for horsepower to bother with all that expense. And it goes on and on because you need premium fuel