Thanks everyone for all the good info.i wasnt sure what the compression was on a stock 400 but was hopeing that useing the 915s and some mill work that i could get real closr to 10-1 comp.i knew that the comp was low but did not realize that it was that low......yes its just going to b a half ass street motor for my 17 year old son.i had some parts laying around so i thought instead of having the 400 crank polished,i would polish a 383 crank and b somewhat better. Lol