Wait till you see what I find....

We had similar issue on 273 while on engine stand thank Christ. Went to set valves(adjustable valve train). Went to set valve clearance while on stand and only get 2 done before it wouldnt rotate by hand. Actually bent a pushrod cuz we put crank sprocket on in wrong spot. We had 3 choices and I put it in the "retarded" position.
Good luck.