Cylinder Head Milled

Hey Guys

In an effort to increase my compression ratio, I am considering getting the cylinder head shaved down a bit. Currently with a new head gasket I am averaging 115 psi. I am concerned that shaving down the head will cause other things to have to be changed such as different length push rods. I have never done this before and am looking for some tips on what I should look out for and consider. Thanks.

If you are now using modern composite gaskets you will need to have the head milled to compensate for the extra thickness compared to the original shim. I started out with a .050 shave to achieve 54cc-55cc combustion chambers, but you should CC the combustion chambers, and then will have the info we need to make a decision as to how much.

You won't need to worry about pushrods until you get into more radical builds.

No expert here, but with normal compression being 175psi, I would be worried about upping the compression ratio on an engine with only 115psi.

Agreed there for sure. I would investigate the reason for such low compression first. Perform a leaidown test on the car and see what the fault of those numbers is. Could just be the head needing gone through or the block and bottom end may be out of sorts

makeing the compression PSI higher via milling can make your bottom end go out sooner if it already has not.

how is your engine? is it burning any oil? consider refreshing the bottom end a little as once you increase pressues others weak links pop up.

your push rods are fine if you hydrolic lifters they will compensate, the solid lifters have adjusible rockers so you just re-adjust them. so .050 should be easily handled by either type of lifter.

My 200 had the smallest large valve cylinder head on it milled .062 cranking compression 215. drove it over 100K after i got the car. No issues prob had close to 100 K when I got it.

Thanks for the info everyone. I hadn't considered performing a leakdown test on the car. It is probably a good idea. Want to make sure there are no leaks before I get the head milled. On another note, I want to test my vacuum pressure with a gauge. I do not see anywhere on the intake manifold to insert the gauge. Where does it go? Thanks

If you have an automatic, that line will do. Also hose from base of carb to PCV would be manifold vacuum.

65 Mustang":1b0keva2 said:

Thanks for the info everyone. I hadn't considered performing a leakdown test on the car. It is probably a good idea. Want to make sure there are no leaks before I get the head milled. On another note, I want to test my vacuum pressure with a gauge. I do not see anywhere on the intake manifold to insert the gauge. Where does it go? Thanks

Click to expand...

A leakdown test is to test cylinder/rings/valve issues, not leaks in the general sense.