I am writing regarding the article about a supercharged GM 350 crate ZZ4 engine ("ZZ4 Power Boost," Mar. '09). I am putting this motor together the way the article was written, but I have come across one small problem: There is no such spark plug as the nonprojected Autolite No. 3935 you used. I want to put the motor together the way you did it. What is the correct plug?
Thomas First St. Peters, MO
The supercharged motor needed a colder plug than those offered in Autolite's standard street series, so we used an Autolite race plug that may not be listed in its standard catalog: PN AR3935 has a 5/8-inch hex, 3/4-inch reach, and a gasket seat. If you can't find the plugs locally, Jegs sells them for $2.69 each (as of July 2009). Competitive alternatives include a Champion C63C or an NGK R5671A-7.
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