I pulled the sparkplugs and valve cover. All valves open up and don't look unusual in any way. However, on exhaust stroke, I notice the intake valves were opened about 1/4 of the way, before the piston fully reached TDC. Is this normal?? Seems a bit excessive as far as valve overlap goes. Could it be my timing chain jumped a tooth? Momentum from the piston and rods and then added heat expansion could, might, hopefully have had a piston tapping a valve? I did also notice a spark plug that looked like it had been melting. I only use premium fuel and never heard any pinging or knocking (till now)...What does the Alfa experts think about this situation?