Spark Plugs MSD 86 CJ7

[TonyF]

RE: Interiors thru the years.

Hi. I have an 86 CJ7 with a 4.2 liter, Holley 4-barrel, MSD 6 and HEI. My spark plugs are completely crapped out after 1000 miles. I noticed a 'pop' in one of the cylinders, pulled the plugs and they looked like garbage. They are gapped at 0.045. Any ideas if they are too cold or too hot? Oh, timing is approximately 6.

 

[n0madic]

RE: Sunday Humor

I just installed a DUI HEI on my 88 4.2liter, Performance Distributors recommends AutoLite Double Platinum gapped to .50-.55. They work very well.

 

[Junkpile]

I noticed a 'pop' in one of the cylinders, pulled the plugs and they looked like garbage

A pop? Like an intake backfire? What did the plugs look like as far as color and amount of deposits on them?

 

[TonyF]

Yes, the 'pop' sounded like and intake backfire, particularly noticeable at idle. The deposits were black to grey and tough to remove with a pretty sturdy wire brush. As for the gapping, I can try to open them up to your recommended ranges and see. I'll let you both know - thanks!

 

[LBR]

The deposits were black to grey and tough to remove with a pretty sturdy wire brush.

Hope that grey color is just carbon and not molten aluminum from the piston. That can prove detrimental to the engine if let go for an extended period. I question the deposits on the plugs and them looking like crap after only 1K miles...not normal for most engines. Any "pinging or pre-detonation" sounds while driving under part/full-throttle loads??? LBR

 

[TonyF]

RE: Laughter.... the color of life

The deposits were black to grey and tough to remove with a pretty sturdy wire brush.

Hope that grey color is just carbon and not molten aluminum from the piston. That can prove detrimental to the engine if let go for an extended period. I question the deposits on the plugs and them looking like crap after only 1K miles...not normal for most engines. Any "pinging or pre-detonation" sounds while driving under part/full-throttle loads??? LBR

I gaped the plugs to 0.45; engine sounds better but at idle there is still a little 'pop'. I haven't heard anything at full throttle. I'm stumped at this point. Any advice? Thanks.

 

[GaryMB]

Sounds to me like it's running rich. If the pistons were melting, there would be more symptoms than a pop and bad plugs...