Maximum compression achieved by skimming the cylinder head?

What is the maximum compression ratio you can get by skimming the cylinder on the 200 or 250cid motor? At what point will you need to modify the stock rods and pistons? Also will you need different lenghth pushrods?

The maximum compression will really depend on which head you are starting with. There are several different chamber styles that vary the combustion chamber size. You'll need to specify which head you are talking about.

Howdy Back Pacer:

To elaborate on Slade's response, the Pre-70 heads typically have a chamber volume of 52 ccs. Later heads have a voulme of 62 ccs. Stock OEM head gaskets are .025" thick while currently available composite type gaskets range in thickness from .045" -.055". All 200 engines have a piston dish. 49 states have a dish of 6.5 ccs, Calif Emmissions engines have a dish of 13 ccs. 200s have a deck height of aproximately .025", while 250s range from .120" to 150". All of these variables will effect CR. All 200 and 250 heads can safely be milled up to .090". After that we strongly advise sonic testing. Decking the block is also something to consider when zeroing in on max CR.

Stock rods and/or dished pistons will not need to be modified for mill cuts up to .090". Different length push rods are generally not necessary with hydraulic lifters. Hydraulic lifters can compensate for up to .125" differences. Adjustible rockers can also accomodate up to about .090".

In all cases where machining and non-stock arts are mixed together it is best to do a pre-assembly and check out everything for clearance, bind and function.

If you haven't discovered the CR calculator on our website go to it and give it a spin. It's fun.

Adios, David