Hot 18mm spark plugs

Richard G. · Apr 7, 2023

Who make a good hot 18 mm plug.
Champions seem to carbon up very fast.
Had that problem years ago with my 39 JD A.
Engine was in great shape and did not burn oil.
About 30 minutes with a brush hog and the plugs were black.
I can't remember what plugs I switched to to remedy that problem.
I sold that tractor years ago.
Now a friend is having the same problem on another tractor.

used red MN · Apr 7, 2023

Sounds to me like the engine was being over fueled.

Dieseltech · Apr 7, 2023

I like Autolite 388, hotter than 386.

Richard G. · Apr 7, 2023

Thanks Sir.
I will tell my friend.

rustred · Apr 7, 2023

I dont think thats the plugs fault.

Richard G. · Apr 7, 2023

I know on my 39 JD A, when I changed to a hotter plug, I never had a problem again.

Fritz Maurer · Apr 7, 2023

Somewhere in the 24 issues of Green Magazine of 98 and 99 this issue is addressed in the mr. thinker column. The JDs seem to be more prone to this due to their speed and compression. Some of the suggestions were, besides hottest available plug , copper wires, keep it around 200 degrees, ignition timing correct, etc. They were also blaming todays gasoline, but since little can be done about that, a true fix is difficult for the parade guys. Possibly contact GM, maybe they can pin point that issue, and maybe other articles that have come along since.

rustred · Apr 7, 2023

well yes hotter to the application, but i was meaning plug brand.

John T · Apr 7, 2023

In the Autolite brand 388 is a tad hotter than 386 and 3116 is close to those but its a NON Resistor which I highly recommend for magneto ignitions...It helps to use shutters or thermostats etc to keep the temp up 180 and higher,,,,,,,dont run the carb any richer than necessary,,,,,,,,avoid long idle periods WORK THEM HARD

John T

Don B. · Apr 7, 2023

It isn't the brand. Champion offers that plug in more than one heat range

r.w.b. · Apr 8, 2023

get hot plugs n gap em tad wider like .27 instead of .25

Loosehandle · Apr 8, 2023

I used to like AC C88L which was also longer but they have recently changed and aren't what they used to be

Pappy · Apr 8, 2023

Read what John T said again. He has it all figured out. That's my system also. Never a problem. I like Auto-Lite.

620 John · Apr 8, 2023

I agree with John T as well. I've had really good luck with Autolite 3116. Running them in the B, 620, and 3020.

J.Wondergem · Apr 8, 2023

Back in the 60's and 70's the brand was the problem. I still don't use them.

Hot 18mm spark plugs

Richard G.

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used red MN

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Dieseltech

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Richard G.

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rustred

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Richard G.

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Fritz Maurer

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rustred

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John T

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Don B.

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r.w.b.

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Loosehandle

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Pappy

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620 John

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J.Wondergem

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