Flywheel Timing Marks

[JonE]

ok, and the 'down the spark plug ole' thing... IF you have the head off, just watching the piston in relation to a metal rule across the top face... and marking its top point - is this just as reliable?

[A G Wood]

Most accurate way is the positive stop method, piston on stop from both ways, marking flywheel periphery each time and and bisecting. There is a lot of 'dwell' at the TDC which makes it hard to get accurate results, even with a DTI. Piece of flat with a bolt threaded into it works fine if the head is off.

[Chris KC]

Accuracy in finding TDC for timing purposes - on a 1930's Austin - is largely academic - you set the thing with engine at TDC 'or thereabouts' and then fine tune on the road by ear. Half a degree either way makes no odds unless you're running a precariously tuned racer, and then you'll know what to do.

Still doesn't answer the question why some (at least 2!) flywheels were unmarked...

[Barry Townsend]

On my RN the TDC marks on the flywheel are at about 11o'clock when the engine is actually at TDC. I'm not sure where the reference point should be on the bell housing.
I made up a little pointer for the camshaft pulley and use that instead, works every time and allows me to use a strobe for fine timing adjustments.