Classic car spark plug needs are fundamentally different from modern vehicles. Older engines with carburetors, distributor ignitions, and flat-tappet camshafts have specific requirements that newer plug technology doesn't always address. Here's what to know.
Copper Is King for Classic Engines
Pre-emissions engines (generally pre-1975) run best with copper spark plugs. Iridium and platinum plugs are designed for computer-controlled engines with precise ignition timing — the loose tolerances of older ignition systems don't take advantage of iridium's fine tip. Copper plugs, with their larger electrode, work better with the voltage output of older coil systems.
Heat Range for Classic Engines
Classic engines often run at different temperatures than their modern counterparts — particularly if the engine has been rebuilt, modified, or fitted with a performance camshaft. The heat range that worked for a stock engine may not be right for your specific build. Consult a shop experienced with vintage engines.
The ZDDP Issue for Flat-Tappet Cams
While not directly a spark plug issue, classic engine owners should note that modern oil has reduced ZDDP (zinc/phosphorus) content that classic flat-tappet cams need for lubrication. Add a ZDDP supplement (available in the Lucas Oil lineup) at every oil change to protect your cam.
Champion and Autolite for Classic Fitments
Both Champion and Autolite maintain extensive catalogs of classic vehicle fitments. If you're restoring a vehicle and want period-correct OEM-equivalent plugs, both brands are the right place to look.
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