ok so im working on my buddies 91 miata it over heated and the head warped . I brought it to the machine shop to see what he could so and the guy checked it out and he ended up shaving off .018. So now my question is now that the compression ratio has changed do they sell oversided head gaskets or is .018 too much to take off and is the head just junk? Or can i just throw it back on and itll be ok with a little more power because of the higher ratio or will the head gasket just blow out?

im not sure what to do so help would be greatly appreciated. Thanks in advance.

 

so long as you don't have any piston to valve clearance issues, I would think it would be OK. You may have to run a higher octane fuel (or octane boost) to compensate for the increased comp ratio.

To check clearance to the valves, you can use an old engine builders trick.....Put some clay on top of the pistons (fairly thin layer, maybe as thick as a nickel, then assemble the head to the engine and hand crank the motor a couple of revolutions. Remove the head and see if the valves left depressions in the clay) If they do, carefully cut the clay perpendicular to the direction of the valve head to see how close the valve comes to the piston.

If your pistons are relieved for the valves (cut depressions in the piston tops), then you need to know how much clearance was available originally in the depression (you could probably use the same clay trick for this as well.)

Good luck.

 

alright so the only thing i should worry about is a clearance issue? Ill be sure to check that. Thanks alot