I am trying to chase down the gremlins before they can cause future problems in my SC engine. I figure that if I can find out what caused the problems that I see, then I might be able to figure out where to look for other problems, and where I do not need to look. Below, I have listed what I have found so far, and what I think are the causes.
So far, I have found badly worn valves and cylinders with a pronounced ring ridge. However, the pistons and bore are still within factory spec below 3/4" below the ridge. Also, the ring lands are worn so that I can pass a 0.010" feeler gauge between the first compression ring and the land. All of the other rings have less than 0.004" play. Also, the camshaft looks very good and the lifters are snug in their bores. The gears under the timing cover don't seem worn and the governor parts are tight.
I presume that the valve and cylinder wear was caused by abrasives entering the engine, since the tractor did not have the original air cleaner when I got it.
Also, I have found that all of the steel backed babbit bearings were badly worn but original, with the exception of #1 connecting rod bearing which was dated 1968. All of the safety wires and clips were in place and undisturbed except for the ones on #1. Also, the #1 throw was out of round and the "new" bearing was worn almost until the babbit was gone on the top side. The tractor had no functioning oil pressure gauge and a new gauge revealed low oil pressure. I checked the rocker arms before installing the gauge, and they were oiling.
I traced the low oil pressure to a stuck oil plunger and it then read 20 psi after I freed it. Also, it seems that #1 connecting rod throw is the farthest bearing from the pump. Thus, I conclude that the plunger got stuck sometime in the distant past (pre-1968), causing the wear on the bearings.
I hope that I have found all of the problems in the engine, but if you have read this far, and can think of anything else that I should check before getting it fixed, please let me know.

MiKesell,, sounds like You done a THourough Chekup , I wouldn't be to paranoid,seems like every sc that I ever owned had to have the intake /exhaust manifold repaired to keep the manifolds from sharing gasses,,. What I do to mine is Lucas Them all up Good ,,Lucas Oil stabilizer in Crankcase ,, Fuel and upper cylinder Lube in Fuel and Or Seafoam ,, If the Tranny leaks put Some Lucas hub seal in there to swell and tenderize the stiff seals ..that stuff worx Great .Other Gremlin Fears ??? you are more than 73 yrs too late to chase down the REAL Gremlins at Case that birthed the sc,,,, Dad always said they were to weak to be a serious workin tractor, and I have to agree ... but they are a sweet little tractor , but to be honest a VAC will do just as much with a hale of a lot more Gusto

Bought a DC that had a lot of wear on the engine parts. Upon further inspection, found a 1/4" hole in the back side of the air cleaner casting. Must have sucked dirt in since new.