Head milling

[akadeutsch]

How much do I need to mill from my head in order to cut out 1 cubic centimeter of CC volume?

[6TIME]

I'd say somewhere around .010"... Considering a .010" 4.0 bore head gasket takes up a bit more than 2cc's.

[Cheromaniac]

Each 0.010" milled from the head surface reduces the combustion chamber volume by 1.4cc, so you'd need to mill 0.007" to achieve your aim.

[akadeutsch]

I would like to get my CC volume down to around 50ccs in order to get my C/R up around 10:1. Anyone see a problem with milling .060 from a 0331 head? Will I run into valve clearance issues? I guess I could always mock up the engine with some clay on top of a piston and run it past TDC on the exhaust stroke, then take the head back off and measure the imprint in the clay. And I probably will do that any how. But it is still worth asking.

[SilverXJ]

There is quite a bit of room before the valves touch the pistons. However, that can vary greatly based on your cam. I don't think you will have an issue but claying is always a good exercise.

[akadeutsch]

I think I will be running the comp 235 cam. It has a little more lift but I hoping it will be fine. I will be using clay just to be sure. Ill report back with my findings when I get the head and rotating assembly back from the shop.

[akadeutsch]

I got my head back today after the mech shop milled .030 off. -.030 was about 5.5cc out of the combustion chamber. I now have ~53.5cc Combustion chambers and about a 9.6/1 C/R. I May call it good here.

[IH 392]

We run the BIGGEST CRANE cam ever made for an AMC six in our stock car, it has the 4.0 valves and custom flat top pistons, the valves don't come any where near the pistons.

[akadeutsch]

Thanks for the info. Who made the flat top pistons for you? I have always wondered why flat tops weren't readily available.

[IH 392]

They're Ford 2300 pistons with the pin bores honed out for the AMC pins.

[akadeutsch]

I have now milled .030 from my 0331 head and I plan to take another .020 off of the block. Do I need new pushrods?

[BADASYJ]

Yes you will need new push rods They are normally good for only .020 tolerance.

[SilverXJ]

I wouldn't go off math alone as the cam base circle can effect push rod length as well. Change from stock rockers and that can effect as well. I would assemble the engine then get an actual measurement.

[akadeutsch]

Good call silver. I have heard that the hydraulic lifters can absorb some extra length but I am unsure just how much. A push rod length checker is only 20 USD from Summit. I will just assemble it and find out

[Hedworx]

I took 30 thou off the bottom of mine, compressed 43thou gasket, Yella Terra 1.7 ratio roller rockers and a comp 68-232-4 cam. I haven't had any issues but I did take 50thou off the top off the valves to offset the extra lift. Maybe that is robbing me of lift now that I know there's enough space in there but I thought it prudent at the time.