i milled some 346s (which is pretty much the same head as a 452 except for changes in the ports ) .055 a few years back and they ccd out at 76cc. i had no problems with them running them on the street for 4 or 5 years until i sold the car. the engine did run a lot better after doing that and a mild home port job. keep in mind that the intake side will need to be milled also.