ya,I just want to over sized valves cause i want to go all out race head. I never drive my shit but for fun.i have put 14 miles on this set up i have now in 2 years..We are realy going to open up the chambers alot.1MM is only 40 thousandth of an inch so that would only be 20 on each side of the valve and it looks like i have that much room all day.I just realy want to make sure it does not effect the valve seat. I can not beleave no one on here has done this before.I am going to do some more checking around.Maybe i will just stay stock size valve but stainless..Anyone ever heard of 21-an stainless ?? they say they have a 1650 degree temp ratting..