i would mill it 20 thousandths, 30 tho max.... you will notice a faster rev and increased top end once the cam gears are dialed in....... my first swap was a sohc vtec engine and with i/h/e cam gears, no cat, milled head, and a good launch on some 13 in vx's i was able to get consistent high 14 sec passes with a best of 14.7 @ 93.4 mph and that was in a 4dr eg! its a great motor to start with