Comp Cams Top Dead Center Stops quickly and accurately locates top dead center (TDC) on most engines. The bolt in style screws into the spark plug hole. The deck plate style is used to find top dead center on engines with the heads removed.
Positively stop piston in order to fine Top Dead Center (TDC)
Bolt-style screws into spark plug hole while plate-type bolts across any cylinder bore when heads are off