Engine Electrical
Distributor Cap
A distributor cap covers the top of the distributor and carries spark from the rotor to each spark plug wire terminal. We list 36 distributor caps from $8 to $277 for 1962-2004 vehicles, from AC Delco, MSD, Bosch and Standard Motor Products, with fits for the Chevrolet Corvette, S10 and K1500, and Mercedes SL500, 300SL and 450SL.
Shop distributor cap by vehicle
Signs a cap is worn
Look inside the cap for burned or corroded terminals, a worn center button, cracks, and thin dark lines called carbon tracks running between terminals. Carbon tracking lets spark jump to the wrong terminal, which causes misfires. Symptoms include rough running, hesitation, hard starting and misfires that get worse in damp weather. Caps wear gradually, so many owners replace them during a tune-up along with the rotor and plug wires.
Choosing a cap
Caps here come in blue and black, in OEM standard and premium replacement grades. Some are vented to let moisture and ozone escape. Check whether the plug wire retainer is attached or whether you reuse your old one. Terminal style matters: wires may push onto towers or clip into place, and the cap must match your distributor. Choose your year, make and model and check the fitment table for engine, since the same model often used different distributors.
Swapping it correctly
Replace the rotor with the cap, since both wear together. With the engine off, set the new cap next to the old one in the same orientation and move the plug wires one at a time to the matching tower, so the firing order stays correct. Line up the locating notch, then secure the screws or clips evenly so the cap sits flat. Make sure no dirt or grease gets inside before you fit it.
Distributor Cap questions
Should I replace the rotor with the distributor cap?
Yes. The rotor and cap terminals wear against the same spark gap, so a new cap on a worn rotor will not perform as well. They are inexpensive and are normally replaced together.
Can a bad distributor cap cause a misfire?
Yes. Cracks, carbon tracks or corroded terminals let spark go to the wrong place or weaken it. Misfires from a bad cap often get worse in wet or humid weather.
How do I keep the plug wires in the right order?
Move them one at a time from the old cap to the same position on the new cap, with both caps facing the same way. That keeps the firing order exactly as it was.