The mechanic adjusted the lifters as far as they would go. Is this the same thing as adjusting the valves? It seems to me that the mechanic threw parts at the problem rather than doing a proper diagnosis. The only reason I go back is because until they find the problem, the owner of the shop is not charging me for any labor and is personally working on my car. I'm just not sure pulling the head is necessary to figure out the problem. He has offered to do a valve job and charge me for parts only but says there is a chance the increased pressure will blow a piston ring.