In a 1997 Chevy Silverado, the distributor cap and Top Dead Center (TDC) are related in setting the ignition timing. TDC refers to the piston's highest point in the cylinder, and it is used as a reference for timing adjustments. The distributor cap houses the spark plug wires, which deliver the spark to ignite the air-fuel mixture. A correctly aligned distributor cap helps ensure that the ignition timing is accurate, resulting in optimal engine performance.