Today I called my local tractor salvage yard looking at my options at locating a engine for my dozer he said that most of his engines has holes in the side of the blocks! out of couriousness I asked him, why? he said "the clean air act" I asked " what does that have to do with holes in the blocks" he said that if a person trades in a old tractor for a new one that he/or she will recieve (correct me if i am wrong) 20% off the new perchase of a new tractor. Has anyone heard of this? How long has this been going on? Can anyone give me more input on this matter? To me, this could eventually hurt a lot of older equiptment owners, and salvage yards, and the list can keep going on and on. THANKS D.G.