A quick and easy way to find very near TDC on any cylinder with the head installed is to OBSERVE the overlap position.
When the cam is in proper timing relation to the crankshaft, and the cam is not greatly worn, and the valve clearance(lash)is correct, TDC will have the valves on the non-power stroke off their seat equal amounts.The exhaust will be nearly closed and the inlet will be just opening, and if the engine can be turned back and forth from 10 degrees before to 10 degrees after the valves will be seen to be slightly off their seat.
This is a good trick to use to verify correct cam timing when a slipped chain/belt is suspected or the proper timing marks are questioned.It works gas or diesel-1 cyl or 20-can be used when there are no cam timing marks-and as Hot Rod Lincoln has repeatedly pointed out is VERY valuable in valve adjustment for finding TDC.
Question if you want, but learn this basic FACT of valve timing and it will benefit you in your engine trouble shooting/repair work.
