Do i need a shim for my shaved head?

[niemczykj]

i had my head shaved because it was warped...turns out the machine shop had to take 18 thousandths off of the head...does anyone know if i will need a shim to make up for that space? or will the shorter head be fine.....i just dont want to get it all back together and turn the key and have the valves all get destroyed if they hit the pistons

[rogoman]

0.008" is the max that should be milled from the head surface. Yes, the valves will be closer to the piston tops which might cause interference. The big problem you're going to run into is the cam timing is going to change considerably which will affect engine operation and might cause bent valves.

You can try looking for a thicker head gasket to try to make up the lost 0.018".

[niemczykj]

the machine shop is gettin me a shim that will go under the head with the gasket...it will cover the difference...i think the shim might be 0.020"...what would that do to performance if the head was on that shim?...less power? less compression?