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One essential key to making reliable horsepower with any type of power-adder is a colder-heat-range, nonprojected-nose spark plug. We used these Autolite AR474 race plugs to avoid preignition problems. These plugs use a very short ground strap with a short heat path to the head to avoid the glow plug problems with projected nose plugs that can cause preignition problems. A nonprojected-nose spark plug is essential for super- or turbocharged engines.