I have lt4 heads with a hyd. roller cam and when the motor was being assembled the pushrod length was check and determined i needed 7.200 pushrods.. Ran it 4500 miles and had pitting in a few valve tips (ferrea valves), so i ground the tips just enough to get rid of the pitting. I checked them now and between the lowest and highest tip there is 30 thousandths. Is this something to worry about? Should I grind the longer valves match the short ones? Any help would be great, thanks