Auto Service World
Feature   July 1, 2000   by CARS Magazine

News – 01-JUL-00 (July 01, 2000)

HIGH-PERFORMANCE PLUGSWhether it's a big-block step-side or a "slammed" Civic, Canadian shops, urban and rural, do encounter modified or high-performance vehicles. If service on these vehicles involve...


HIGH-PERFORMANCE PLUGS

Whether it’s a big-block step-side or a “slammed” Civic, Canadian shops, urban and rural, do encounter modified or high-performance vehicles. If service on these vehicles involves a plug change, a few facts about plugs and their working environment can head off potentially serious trouble.

Cylinder temperatures are key, as the higher temperatures inherent in high-performance engines can crowd the upper limit of pre-ignition conditions. And pre-ignition in highly tuned engines can knock quarter-sized holes through pistons in a single high-speed pass. Avoiding that kind of blow-by often involves conservatively “cold” plugs, but on streetable vehicles, fouling on a cold start is all too likely, especially with carbureted engines. What’s the answer? There isn’t necessarily any easy solution to driveability in tuned dual-purpose vehicles, and in early or pre-electronic ignition engines, spark voltages may fade noticeably at high RPMs, further complicating the problem. One suggestion which can help both high revving performance and fouling issues is a coil upgrade. High output coils can partially compensate for point or early electronic systems not designed for sustained high RPM operation, but for the technician, they offer an important bonus. By improving the ability to fire lightly fouled or wet plugs in a cold start situation, they allow the use of colder plugs, buying a little insurance against pre-ignition. Regardless of other modifications, if you’re playing with heat ranges, it’s wise to err on the cold side in high performance plug selection.


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