Spark Plugs for Minneapolis Moline

I would like to know what spark plugs are used by the different models, I am looking at only the Magneto run tractors or Letter Series Tractors.

I would prefer not using any Champion Products, since their quality is very poor, it has been that way at our farm at least. No where near the quality of the old Champion Common spark plugs I use on many of my old single cylinder engines.

Auto Lite is my first choice with Denso or NGK coming in after that.

I would like to know what temperature range means, a lot of folks out here talk about hotter plugs or colder ignition plugs, but no one explains why or the application on why they use a hotter plug.

Champion and Autolite have a few pages dedicated to educating you about spark plug applications, but unfortunately they never cross reference older equipment, and when they do it is just a list of numbers and letters.

I am a Land Surveyor, not a mechanic, I understand the old Make and Brake ignition system very well. When it comes to surveying a line for 16 miles, piece of cake, but when I go to Napa, Autozone or O'Reileys I get a high school kid that has no clue about plugs for older applications unless it is a Honda, Toyota that he street races.

Thanks
 
Any plug of 14mm with a 1/2 inch reach will work in a Z or R. recommended plug is a Champion J8 I prefer Autolite.
Not for sure on the U or G. You will have to check the old plug. Some take a Champion D16 which are common and I believe
one of my U tractors take a W-12, this is an expensive plug and a large one.
 
Stay away from any Champion plug. Rebuilt a 1939 UTS lately. Wouldn't even start with
Champions. Put in set of Autolite and fired right up. Had a Jetstar 3 last night with a set
of NGK's which looked new. Would only fire on outside two holes. Put in proper set of 386
Autolite and runs smooth. Champions seem like too cold of a plug for MM's
 
I always put Autolite in my molines there is 3 plugs that you need to know
R and Z 14mm head is 437
U G 18mm head is 3116
7/8 the big ones is 3076
 
My experience has been just the opposite of what I read here. I tried Autolite and was constantly having a dead one. Could not get in over 2-3 pulls before plugs started going dead. Put in Champion and use them for years. As far as heat range: It refers to how hot the spark is when it jumps from the electrode to the ground on the bottom of the plug. Cold plugs will have a short insulated electrode; hot plugs are long. They both are the same overall length; electrode extends further into the plug body or housing. Generally: hotter plugs are advised in low compression engines; engines that may burn a bit of oil; and low octsne gas or "distillate". Colder plugs are less likely to try and predetonate in very high compression engines or under long high power periods. If I get plugs for a gas engine Moline (not one with high compression heads) I will go with a D-21. (very hot plug---also this is the old champion number; do not remember the new numbers) Higher compression or LP: about a D-16. These are for the more widely used thread size; if your engine has the big, older plugs in it; you are very limited as to the plugs available. I have run the D-9 (coldest plug made) in some of my pullers with no problems. A lot depends on the engine specs.
 
I suspect that hey are all junk to some extent but in U's ans G's, Ive had better luck with Autolite 386s or AC-C-87's. In fairness,though I've had trouble with Champion, I've removed rusty old ones from tractors that ran just fine.
 
The heat range of the plug refers to the rate at which combustion heat on the center electrode tip is transferred in to the main body of the plug. A longer distance slows down the heat dissipation process and keeps the tip hotter (while at operating temp). Not a factor until the plug heats up, no difference on a cold engine.
 
I agree with you on Autolite plugs. We call them AUTOLITE BUT WON'T. But you explanation on hot versus cold is not right. A hotter plug does not produce a hotter spark. As you say the porcelain is longer in a hot plug. So the heat travel from the tip of the plug to the engine block is longer to get cooled. Therefore the tip is hotter and will cause pre ignition in a hard working engine or burn off deposits in light duty or old and oil burning engines. This is also why the plug seat should be clean and plug should be seated firmly and tight. So the plug can cool properly.
MMDEL
 
in many years of testing and building engines I have had the best results with autolite plugs heat range is very important based on compression and fuel you may be using, with a little work your engine will tell you what it likes.
 

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