Dave, actually passed it through and then ate it. The original head pushed the guide..It took a long time to believe what I had found (no valve lift, no cam lobe). Then , the stubborn type, I disassembled the pushed guide . You cannot buy replacement guides ( hint, hint BS knows). So I measured everything (e.g., od of guide, id of guide hole), and reassembled. The engine ran ok until the pushrod went into the pan. This , I believe, was not related to the pushed guide, maybe poor valve adjustment? By then BS had sent me a new head fully assembled. After the second tear down and reassembly I have not had a problem, but I did put an oil cooler on the tractor. Also a head temp probe. I will post the head temp soon during worst conditions:85F, 3 bagger full of grass, on grade. I believe the head overheated and softened the aluminum, loosening the head grip on the guide.
Old timers are tired of my theory. Perhaps Briggs received a bunch of bad heads (alloy, heat treat). The pros are afraid to speak , especially those with ties to BS, and I understand. There have been responses from them that my experience is not so unusual. If you guys are handy or used to working car engines , the tractor engines are cake, no hoists ,etc.:tractor: