I'm replacing my head gasktets in my Buick and decided to clean the valve lifters. I sprayed Berryman B-12 Chemtool in the hole on the side and on top of the valve lifter. I was in AutoZone today and asked what they recommended for cleaning them. He said I'm going to have to replace them now because I sprayed that stuff in there. At $16 a peice, it will cost me $266 to replace them all.