I have used the technique of finding TDC suggested to you by Carl D. It
works well and is quite easy to do. If a degree wheel is not available
or too difficult to assemble to your crank you can make marks on the
crank pulley. TDC is halfway between the mark you make on the pulley's
circumference where the piston goes against the stop in the spark plug
hole while turning the engine in one direction and the mark made when
turning in the opposite directon.
Incidently you can make marks on your crank pulley that correspond to
degrees before top dead center (BTDC) once you have a mark for TDC. You
do it with a tape measure marking off the distance in inches (or mm)
equivalent to the angle BTDC. You calculate the distance by first
measuring the diameter of the pulley, compute its circumference and the
take the fraction of the circumference that corresponds to the angle
BTDC. The fraction of the circumference is the angle BTDC divided by
360. The distance for 10 degrees BTDC on a 6 inch pulley would be= (pi
x 6) x 10/360. The answer in the example is 0.524 inches or "just a
little over 1/2 an inch".
There is a problem with using the Carl's TDC technique on an F head
engine like a Coventry Climax because the spark plug hole never "sees"
the piston being well off to the side away from the piston.
Regards, Tony Souzaep
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