To determine true top dead center (TDC) of the engine, you'll need to install a piston stop of some sort. If you're building your engine from scratch and don't have the head(s) on yet, it's easy to install a piston stop, such as the one we're using here. Alternatively, you can install a different kind of stop through the spark plug hole. The degree wheel kit's pointer can be installed now as well. Rotate the crank to approximate TDC, align the pointer with the TDC mark on the degree wheel, and tighten the degree wheel to the crank.