New question. Figured out that the exhaust valve was stuck open preventing proper valve adjustment. I bought a new head , both valves, oil seals and head gasket. I reused the retainer clips, springs, posts, valve guide and rockers from the bad head. Had the new valves put into the new head then I installed the new head and did the valve adjustments. Pretty straight forward. Torqued the head bolts at 19 ft lbs (per John Deere mechanic). Definitely have power back and the blades are running like they used to but . . . now the low oil pressure light comes on about halfway through my 1 acre yard. If I turn the tractor off for 10 min then power it back up I can mow for awhile again but the low oil pressure light comes back on. Could I have done something to cause this when I put the new head on ? Or could it just be a coincidence like a clogged or partially clogged oil filter ?
*edit* Now that I think about it, it's been quite awhile since the oil filter was changed. Should I try that first ?