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tubman · 08-19-2020, 09:49 PM

"L" series Champions and equivalents are too short and "N" series are too long. That's the conclusion that was reached before. The "L" series will be shrouded, but not as bad as stock plugs. I believe the proper plug is an "N" series with an appropriate spacer.

Years ago I ran some marine surface gap plugs in a 276" Merc with Offy heads and an MSD ignition. The surface of the plugs were flush with the inside surface of the head, and they worked great. They were designed for an electronic ignition system that produced a very hot spark. The MSD was up to the task of producing a hot spark, but it would eat the coil wire tower in the distributor cap in about 6 months, requiring cap replacement.

08-19-2020, 09:49 PM	#9
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,316	Re: AutoLite 216's in Offy heads "L" series Champions and equivalents are too short and "N" series are too long. That's the conclusion that was reached before. The "L" series will be shrouded, but not as bad as stock plugs. I believe the proper plug is an "N" series with an appropriate spacer. Years ago I ran some marine surface gap plugs in a 276" Merc with Offy heads and an MSD ignition. The surface of the plugs were flush with the inside surface of the head, and they worked great. They were designed for an electronic ignition system that produced a very hot spark. The MSD was up to the task of producing a hot spark, but it would eat the coil wire tower in the distributor cap in about 6 months, requiring cap replacement.