Finding top dead center (TDC) can be a bit more tricky than most people might think. It is impossible to accurately tune an engine without finding TDC precisely, because it is the primary reference point on which you base piston-to-valve clearance, ignition timing and cam timing. In other words, finding TDC is vital.
Finding true TDC is a fairly straightforward operation, but it does contain some nuances and subtleties that can be confusing. To accurately find it, youll need a few tools: a degree wheel, a piston stop, an indicator and a crankshaft nut. This procedure can be done with the heads on or off, but the type of piston stop youll need depends on whether or not the heads are installed on the engine. A screw-in-type stop threads into the spark-plug hole, while the other style attaches to the deck surface of the engine block.