I am dismantling my 1929 coil engine for rebuild and have found that there are a number of timing dots marked on the gears. Is there a simple way of checking for the correct positioning with out relying on the marks?
Incidentally, I found out why the engine smoked a little; the piston ring gaps are 0.043" instead of about 0.005"!

Open to correction here but I think you should find that with no.1 on TDC compession, both valves on no. 1 should be shut. If you rotate the engine back and forth, probably inlet and exhaust valve should both start to lift a similar number of degrees either side of TDC (see flywheel), unless you have a funny cam profile, unequal valve clearances or asymmetric tappet base curves. For real accuracy use a dial indicator on the valve head but I think you can feel it with your finger well enough to know if you're somewhere near.

Regards, Stuart

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Stuart,

Pardon, but your slip is showing. I think you omitted to mention that it was actually the valves on number four that were 'rocking'. The valves on number one are of course tight shut. (Between squeeze and bang!)

There are fifteen degrees of overlap between Inlet opening at TDC and Exhaust closing 15 degrees later at 15 ATDC. (Between blow and suck)

As you rightly say there may be some small discrepancies due to tappet clearances, follower shape, or cam profiles but the principal is the same.

For the record (and according to the Companion) the standard valve timing is ........

Inlet opens at TDC
Inlet closes 40 deg ABDC
Exhaust opens 45 deg BBDC
Exhaust closes 15 deg ATDC

Mike

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One further thought.

The 'smallest' amount that the timing can be out is one tooth on the thirty tooth camshaft wheel, which is twelve degrees. This represents two minutes of time on a clock face which is a stonking amount and should be fairly obvious when installing.

Mike

Thank you, Mike, brain fade again!

Regards, Stuart

Many thanks to all for your help. At the moment the block is off so there are no valves to observe but I can do the check with a dial indicator on the camshaft lobes.
Regards
Brian