I have a pair of 186 double hump heads with 1.94 valves and 64cc chambers. I want to put them on my 350, but the semi closed chamber with factory flat top pistons would give me a 10:25:1 compression and I want more like 9:5:1 so I can run 87 octane. Can I get my heads cc'd to 72 or so at a machine shop or can I do it myself? How much does it cost?

Thanks

Not sure how much it cost but it can be done !! You need to have the chambers deshrouded on both intake and exhaust ,this will actually improve airflow as well. If you run a .040 gasket and deshroud the chambers you will be WAY OK.
Another thing you can do at home is just polish off all the casting marks in the chambers.Alll you need is a porting grinder and some stones,or abrasive rolls.

If it is still a stock short block, you will be right at 10 to 1 CR. w/ the old stock, .020" thick steel shim headgaskets so I wouldn't worry about it!

GM spec's it at 10.25 and I figure that is blueprinted so not blueprinted, it is like 10 to 1!!!!

pdq67

PS., I mention still being stock b/c our piston "dith" is about .025" stock so .020" shims create a good .045" quench!!

Do you think 10:1:1 compression will run on 87 octane without detination? I have always thought the rule of thumb for 87 octane was around 9:5:1 compression.

Thanks

[quote=Erics69;1436606]Do you think 10:1:1 compression will run on 87 octane without detination? I have always thought the rule of thumb for 87 octane was around 9:5:1 compression.

Thanks[/quote

I doubt it would work without having to back the timing off, aluminum heads maybe but I doubt the irons will take the compression at 87 octane.

Steve