39 John Deere A

shanedog · Sep 25, 2014

I have a 1939 John Deere A that I need help with. The tractor has about 45 horse on dyno and the motor has alot of head work and carb work with .125 over pistons with stock crank and cam. The tractor runs good until it gets into a real hard lug right at the end of the hook, it kinda seems like it just falls on its face. What you guys think the problem could be? Could the cam just need a refreshing or is it something else? Thanks

BushogPapa · Sep 25, 2014

A lot more questions need be answered, but if the rear tires are not slipping, you are running out of Motor..

More Stroke and a better Cam will help, but +125" is not helping very much..

Maybe go to 5 3/4" bore or 6 1/8" along with a serious Stroker crank..

Ron.

BushogPapa · Sep 25, 2014

A lot more questions need be answered, but if the rear tires are not slipping, you are running out of Motor..

More Stroke and a better Cam will help, but +125" is not helping very much..

Maybe go to 5 3/4" bore or 6 1/8" along with a serious Stroker crank..

Oh, that is for a lowly "B"..!
Bet you can find more for an "A"..!

Ron.

Josh Blackburn · Sep 25, 2014

A cam is a very good upgrade. If you have a opened up carb on a stock low lift cam it's hurting you. Give me a call and I can help you 9892775366

toot · Sep 26, 2014

Cam will help, but you have to go massively to the internals to get it out. It would also help if you said what kind of class you are running, tire size, etc. 45 horse is not too bad for a farm stock kind of class. If you are truly using the stock crank, your stroke is only 6 1/2 like the unstyled. A crank from a 41 to 46 model is 6 3/4. That will give you a little more lug and compression. If you are pulling a non cut tire in a farm stock type of class with a 18" high drawbar, I would change the crank, cut the rockers and play with the timing.

shanedog · Sep 26, 2014

Im running stock 4500lb and 5000 lb class with 15.5 tires. It always hooks up really good just the motor runs out of power the last couple feet of a pull and im just out of top 3 everytime by that much. thanks

toot · Sep 29, 2014

So it has the smaller 6 1/2 crank?

shanedog · Sep 30, 2014

yea has the smaller one. The longer one is a direct replacement or does anything need to be swapped to make the longer one work?

toot · Sep 30, 2014

Rod and main jounals are the same. If your rods are babitted you can adjust, same with mains. If your rods have inserts, you will have to size them. This swap Alone will increase compression and torque. Other mods may be needed, but I would definately do the crank first.

39 John Deere A

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