1951 M crank?

Anonymous-0 · Nov 1, 2012

our FFA is doing a 1951 M it's crank measures 2.495 and is in good shape wondering if it had at one time had the smaller crank in it and what bearing size should we order for overhaul and was there a difference in the rods? thank you Jerry

El Toro · Nov 1, 2012

That measurement you posted is for the H model Farmall. Prior to S/N 278050 your main journal should measure 2.7474"-2.7485" after that S/N they should measure 2.8075"-2.8085" for the Farmall M's. Look in your manual. Have your machine shop to measure your crankshaft. The measurement you posted shows .252" of wear or machining. Make sure you 're working on a Farmall M. If have an H Farmall your shaft isn't worn. I would have it polished and buy your bearings from that machine shop. They will also measure the rod journals. They won't grind it undersize unless it needs it. You need to make sure you have a Farmall M. Hal

D Slater · Nov 1, 2012

Standard rod journal size for M tractors that have a crank cast number ending with D, DA, DB or DC is 2.4975 to 2.4985. DD or DE suffix cranks have bigger journals. Same connecting rods work with both cranks. Bearings are just different thickness. You have the small journal crank and if round, smooth and no taper it should be fine. Just get bearings for a engine below the serial number break. Off the top of my head I think its engine # 278050 in a M tractor.
.006 max. clearance was allowed on a used crank if not egg shaped or more than .0015 differance in diametter across the journal. If that checks out .0045 would be better to stay at or under. Measurements of all parts is the only way to know whats needed. Should be able to use standard or .002 bearings though. Lots of old M tractors running over the ideal new clearances. If its going out and work all the time and needs to last to the next piston or ring job, ideal may be the best.

Earl-IL · Nov 1, 2012

The correct spec. for early "M" for the rod journal is 2.4975--2.4985 main journal is 2.7475--2.7485. If you have the crank out I would recommend grinding crankshaft.IF YOU WANT TO TAKE A CHANCE!!!! you might be able to use a .002 under rod brg. Just remember if you buy a bearing and you install it and it is too tight, there is no return. So buy one .002 bearing & try it on journals. email me if you need more help. Earl

El Toro · Nov 2, 2012

I thought you were referring to main bearings. You also need to measure those journals. The rod journal measurement you posted is ok. Take the crankshaft out and have your local auto machine shop to measure it. Even if it's worn a few thousands you can get undersize bearings.
They won't grind it undersize unless it needs it.
They may recommend to have it polished. The machine shop will furnish the correct bearings. You can replace the clutch if you pull the engine
or have it rebuilt. Hal

1951 M crank?

Anonymous-0

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El Toro

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D Slater

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Earl-IL

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El Toro

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