Milling head good or bad?

Ok i have a 99 si with 10:2:1 compression. I read that the Civic type R has 1O:8:1 compression. So i am currently buying type R cams and going to port and polish my head. I was wondering if it would hurt my head much to raise the compression to that of the type R. Thanks for the help

I noticed in your signature that you are planning on running a healthy shot of nitrous, in which case raising your compression by any means is not a very a good idea.

raise the compression with a thinner gasket or pistons. shaving the head is irreversable... if you should ever warp the head or block from overheat, you may not have enough clearance to redeck it back to flat, and will have to plunk down a lot of change to replace it.

higher compression is ok in Japan cuz their gas has higher octane than ours.

Agreed with the above posts. You can get away with it, and see some nice power increases across the rpm range from it, but it is risky. You have to tune very carefully, it is irreversible, and I know of far too many stories of cars blowing head gaskets from poor machining, or being stuck running with thicker head gaskets (to re-lower the compression ratio) or racing fuel to stave off detonation.

Use a method like drift described over this option. Your cheapest option is the thinner head gasket.