440 recommended spark plug

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TheScottFraser
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Joined: Sat Jan 24, 2015 2:49 pm

440 recommended spark plug

Post by TheScottFraser »

Before I simplyreplace the plugs with the same thing that I take out. What should I be running in my 440's on our 39AC?
1985 marinette 39AC
1988 Oday 272 sailboat
1986 Boston whaler 13'
And more motorcycles then could ever be deamed appropriate.
The Captain and I live in woodstock, Ga.
Our boat is on Lake Lanier
martindesign
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Re: 440 recommended spark plug

Post by martindesign »

I'll start with this. I hate champion plugs, they don't run well in alot of applications. Even though they make plugs for alot of other names. With that out of the way, champion plugs are the only thing that runs right in Chryslers. I wouldn't try any platinum plugs. The resistance and gapping of the OEM replacement on champs is designed for that ignition system. Have ur local parts store look up the correct heat range and style for ur year. I know they used a few diff. Heads over the years on 440s. Hope that helps.
Machanic, fabricator, carpenter, plumber, electrician, designer, hotrod builder and glutton for punishment. :ugeek: current boat; 1969 Marinette 32 express bridge 440's
Catawba Oh
javalin390
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Re: 440 recommended spark plug

Post by javalin390 »

I've studied gasoline engine performance for many years. Here's some words of advise from Dr. Christopher Jacobs, Ph. D E.E. , founder of Jacobs Performance Ignition Systems. He breaks spark plugs down into 3 basic types, by brand, if you will. Having to do with the hardness of the metal that the plug is made of. The hardness will determine the rate that the electrode on the bottom of the plug will deteriorate over the life of the plug. The rate of speed that they deteriorate, determines how well they fire in various circumstances, i.e. fowling, overheating, lugging the engine, etc... Champions, use a low carbon, soft steel, that although will fire in adverse conditions, tends to burn the electrode off the bottom very quickly if run hard or detonating. And since Champ's are specified in most cases by Mopar, require tune-ups quite regularly. Next in line are AC-Delco's. They have a harder metal, can withstand more punishment, have longer life spans, but...with this comes the need to keep the engine in top tune all the time. Simple things like dirty, corroded distributor cap terminals or bad plug wires will cause noticeable performance problems. Last in line are Auto-Lites. The hardest of metals, they can take a beating, but again the engine has to be in top tune all the time. Being a former GM mechanic, I'm pretty biased toward Delco's, which is what I run in my 360's. I simply take the factory recommended Champ number and cross reference it to an equivalent Delco. I'll agree with Martindesign's assessment not to use fancy platinum plugs, as there is no real benefit. They may work well in a modern aluminum overhead cam car engine, but would quickly self destruct in a boat !!
Jim Elias
1974 37' SedanFlybridge
Twin 360 Chryslers.
Marblehead, Ohio
martindesign
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Re: 440 recommended spark plug

Post by martindesign »

Good input Jim. I agree with everything he said. I've run platinum plugs in newer hemis and they code for misfires same as the immediate power loss in ls motors if anything but delco being run from the knock sensors pulling timing.
Machanic, fabricator, carpenter, plumber, electrician, designer, hotrod builder and glutton for punishment. :ugeek: current boat; 1969 Marinette 32 express bridge 440's
Catawba Oh
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