Ignition Timing Basics

What is Top Dead Center (TDC)?

Top Dead Center (TDC) is the point where the piston reaches the top of its stroke in the cylinder. This is a critical reference point for timing measurements.

When we say "20° BTDC," we mean the spark plug fires 20 degrees of crankshaft rotation before the piston reaches TDC. This gives the fuel-air mixture time to ignite and build pressure before the piston starts its power stroke.

How Advancing Timing Works

Advancing timing means firing the spark plug earlier (more degrees BTDC). This can improve performance at higher RPMs because:

The fuel-air mixture has more time to burn completely
Peak pressure occurs closer to TDC, maximizing power
Higher RPM engines need more advance to compensate for faster piston speeds

Warning: Too much advance can cause pre-ignition (knock), which can damage pistons, rods, and bearings. Always verify timing with a timing light.

Safety First

Never advance timing without proper safety components (billet flywheel, billet rod) if you're running high RPMs. Always verify timing specifications with a timing light and listen for detonation/knock.