440 source/push rod clearance issue

i had the same problem with my 440-1's after I went to a 7/16" pushrod. they only touched on lash which kept it at zero. I ran the motor a few times to get the witness marks on the heads. I removed them and clearance them with the air grinder and carbid bit and wd-40, it keeps the bit from loading up with aluminum. manton will make you a pushrod with thick tubing in a smaller diameter so you don't have to grind the heads but will cost a lot more than grinding.