Changing the subject a bit, I want to make sure I have my motor on TDC to set my timing marks on the flywheel. This is my plan, tell me what you think. I'm building a fitting to screw in the spark plug hole, and running a vacuum line to a small syringe (like a insulin syringe). I can eyeball the rotor location close to TDC, the install this contraption and rotate the motor so the syringe moves out to the end and starts back in. then back the motor up again till the syringe tops out. I figure that aughta be an accurate TDC. Whadda ya think???

Bob Mears
Supermarine Spitfire

 

On a new engine full of assembly oil it might work. Otherwise, they leak compression like an open screen door. Just stick the vacuum line in your mouth with your tongue over the end, and rock the engine back and forth over suspected TDC. The null in suction is TDC within one degree.

 

Lynn E. Hanover

 

Its after 11:00 PM. Where is your TDC?