yea this is my first race motor and i got these heads in a trade so i'm running them for now, i had a 355 but it was just a 10 to 1 motor and i shifted around 6500 rpms. the 383 is about 12 to 1 and last year i was so scared to shift it over 6800 because i didn't want to blow it up. but the car ran ok at 6800 rpm's but i never try it any higher and it's killing me to know lol!!!