Does anyone know how high you can raise the compression of a lancer 1.8 4G93 by machining the head. I obviously dont want the valves and pistons to interfere.

Who ever is doing the machining work should be able to work it out and tell you.

If they can't then grab the head and get as far away from them as you can.
Then find a compentent engine or head builder who knows what thier doing.


But if you did shave enough off for the pistons to interfer with the valves then it will never run anyway. I doubt it would start on desiel, let alone petrol, and if it did the C/R would be so high it would detonate itself it pieces very quickly anyway.