A degree wheel is not needed to verify that the TDC mark on the dampener is correct. A piston stop can be used & one can be purchased, or made from an old spark plug. Install the stop in #1 or #6 cyl & rotate the engine CCW slowly until the piston hits the stop. Mark the '0' spot on the damp. Now rotate the engine slowly CW until contact is made with the stop. Mark the '0' mark on the damp. TDC for that dampener is halfway between the two marks. It is a good idea to back off the rockers on the cyl used for testing, to avoid valve/piston stop contact which can occur on some engines.
