JD A Spark Plug gap

[JDRandy]

I've got new Autolite 386 spark plugs for my 1943 John Deere A. Can anyone tell me what I should use for the gap setting?

 

[Mike M]

I run them at .035" even though they are to be around .030" ? or something.

I also run the hotter 388 plugs. Found out here these are resistor type, but they have not given me any troubles.

 

[Christopher S.]

I don't have the book in front of me but I believe that they should be set at .030. Those 386's are a fairly cool plug, maybe step up to 388's, or if you want an amazing plug go for autolite 3116's. The difference they made in our B was amazing.

 

[Paul from MI]

I use Autolite 3116 plugs in my A,B, & H. 388's are resistor type which doesn't work as well with a magneto. If you only parade and show the tractor you will eventually foul anything you use. If you work it and keep the temp up, 386's will work fine. I usually gap them at .030", but it's not that critical.
Paul

 

[Duane Larson]

JDRandy,
I don't have access to my Field Service Bulletins now, but as I recall from one in the '30's Deere suggested opening the gap to I believe 0.040" prior to taking to a fair to demonstrate because it improved the idling. With a good magneto I run mine about 45 to 50 for this reason, and they seem to pull fine when plowing as well as idling and parading. But you need a magneto with a good coil to provide the necessary high voltage to jump the plug gap.