Spark Plug type

Criswell":1ivbk7t2 said:
Just a quick question; You have two different plugs listed, the Autolite 386 and the Autolite 3116, the 386 is a resistor plug while the 3116 is a non-resistor plug, which one is being used? The 3116 (from Autolites own literature) runs just slightly hotter than the 386, not by a lot. If the D-21 plug is too hot and the D-16 is too cold, why not try the D-18? The range of the D-18 would be right between the other two.
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I use the 3116's, I misspoke when I said 386's. While the D-18's would probably work fine, I'm just not a fan of Champion plugs, or should I say I'm not a champion of Champions. :D Back in the day I worked at an auto parts store and sold AC, Champion, and Autolite plugs. One of my best customers had a thriving tune-up shop, he was well respected with a fine reputation only used AC plugs, once again, go figure. In the overall mix of everyone's experiences I'm sure it doesn't matter which brand you use as long as it works well for your machine. Like Jim says engine condition is a factor as well. Here's the link to a previous discussion on spark plugs; viewtopic.php?f=1&t=79777


Don McCombs":1ivbk7t2 said:
Smokeycub":1ivbk7t2 said:
I feel the D-21's are too hot for my Cub ...
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Just curious, what makes you think this is the case?
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I remember (again from back in the day) that one should run as cool of a plug that the engine would tolerate and still burn clean, too hot and they would cause detonation, but that was in higher compression engines than an F-Cub with 6:1 compression. Detonation can cause a number of problems especially with aluminum pistons, not sure how much of an issue this is with F-Cubs or the higher compression C60 with aluminum pistons. As a rule of thumb higher compression engines require cooler plugs, i.e. a 65 289 HiPo called for BF32 Autolite plugs and a 65 289 2V called for BF42 plugs, or a 70 454 4V called for R44TS AC plugs and a 79 454 4V called for R46TS - the major difference being the compression ratio on the 454's, the 79 having been "de-tuned" with less compression than the 70 by about 2 points.

FWIW - I am no expert on Cubs (I've had Smokey for about 8 years - doesn't smoke anymore - and I've been around the barn a time or two with him), I simply try to respond on subjects I've had experience with and hopefully help someone out.
 
My money is spent on Autolite 386's and 3116's.

I do have one set of D21's in a Cub I purchased this year and it is doing fine.
 
An interesting note... In the Common Cub Questions section I found some info on plugs http://farmallcub.com/phpBB2/cubfaq.php#6 It shows D21 and D16, no mention of D18Y. Autolite's 3116 plug crosses over to a Champion D18Y in Champion's cross reference, both non resistor plugs, and Autolite's 386 crosses to a (R)D16, both resistor plugs. When one crosses a 386 back to Champion it comes up with D21?? Please note - cross references are NOT and an exact science, they usually are accompanied by some sort of disclaimer. The Autolite application catalog calls for a 3116 for all Cubs except the Industrial Cub which calls for a 386. Autolite's 388 seems to cross to D21. The NAPA lookup (since I can't find a Champion lookup for farm tractors) says that Champion calls for 593 (new numbering system) which is a D18Y and that crosses to Autolite 3116, NAPA lists the Autolite 3116 as well. farmallcubforever.com recommends D21 Champion plugs as well as lots of folks here on Farmall Cub.

So, not to kick a dead horse, it's whatever plug suits you and your Cub.
 
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