The Minneapolis-Moline M-670: A full-featured 70hp tractor from the 1960s

Jan 12, 2017

The M-670 is built like a tank and fun to work with

IN THE SHOP with Rachel

By Rachel Gingell
Farms.com

We’ve got a Minneapolis-Moline M-670 in the shop right now. It’s fun to work on and will be a great tractor once we get it fixed up.

My dad bought this M-670 “some assembly required.” More than 14 years ago, the soft plug had rusted out of the head (more on that later) and needed repair. The owner, a recent retiree, disassembled the tractor in the garage and then stopped working on it. Perhaps removing the head was more work than he’d planned or maybe he just lost interest.

Over the years, the past owner gathered all of the parts needed for the project. But, the longer he let the project sit, the more difficult it became. Eventually, he decided that the project was too big for him and listed it for sale. By the time we got to it, the engine had been disassembled for 14+ years and the pistons were stuck solid.

The good news is that we got a great deal on the tractor so the work is proving worthwhile. My Dad knows a lot of tricks to get pistons un-suck and we used all of them on this tractor. The project isn’t finished but we’re well on our way to success.

The part that failed and started the whole problem here was the soft plug, a smart design that keeps the engine intact if the fluids inside freeze and expand. Instead of cracking the block or head, the soft plug (which you might know as a “freeze plug”) expands to release the pressure. The M-670 is one of many tractors with this smart design.

Minneapolis-Moline M-670
Photo: TractorData.com

You can save money by buying a tractor with a blown soft plug and replacing it yourself – but be prepared for an intensive job! This isn’t for a beginning mechanic. You can prevent this from happening by keeping your tractor from freezing solid in the winter.

I’m looking forward to getting the M-670 together. It’s a great tractor with a full range of features. Ours is a Super M-670, which is a great upgrade from the standard. The M-670 comes with diesel, gasoline and LP fuel options.

The only criticism I could possibly offer is that the spacing on the ampli-torque transmission isn’t the best and can be awkward for plowing. For such an economical and reliable tractor, though, this is a small price to pay.

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