Valve Grinding 4 Engines - InstructablesNov 30, 2007 . CONSIDER DO YOU NEED TO GRIND VALVES ? A . to begin with do a compression check and note what cylinders are low 20 or 30 %,(example some are 85 and some are 120 lbs.) AND THEN B .examine the movement of the valve lift before deciding to remove head see? if valve motion is moving like.why do we grind engine head,Cylinder head work - grindingDec 10, 2014 . I remember one time seeing a cylinder head grinding machine that had the stone in the table and they just moved the cylinder head over it by hand and had no need to . I keep wondering if one of these days I'll see you have hired your first employee, because you are too busy to do all the work yourself.