Don, without actually mounting a degree wheel on the front of the crankshaft, it's an educated guess as to where timing marks are going to be on a particular engine. Even the engines with more accessible timing marks than a stovebolt can have timing errors due to manufacturing tolerances between the crankshaft, flywheel, bellhousing, etc. Does your timing light have a delay-flash feature which allows you to dial the timing flash back to zero with the engine running? If so, all you would need to do is find a true TDC position by using a positive stop on the #1 piston. Someone else just discovered that the positive stop rod inserted into the spark plug hole needs a bend in it to actually be able to reach the piston crown. If you need information on making the stop fixture and doing the checking procedure, drop me a PM- - - -it's a pretty detailed process.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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