farmall m confusion...

rdenny121

New User
i am in the process is restoring the familys farmall M . but im am majorly confused on what engine is in the tractor. i have been doing tons and tons of reserch and seems i keep hitting walls. the information i have right now is pretty little but hopfully somone can help me out, ill post what info i do have and see if anyone can make any sence of it.

I am pretty sure it is a 41 from the serial number tag.the engine serial number tag is half missing i thing the only visible numbers on it are "5-7-J" that is below number 1 spark plug. The other numbers on the block are "6943-DJ" and "C-248", those are below number 4 spark plug. I do,have the engine torn down and cleaned up and ready to go,back together. Another part of the confusion is linked to what im trying to figure out, the pistons are 4" and are domed, from what i got that they are high compression pistons. I found a kit on this site for a major overhaul, but am not sure if it correct because it asks for serial numbers.... any info would be greatly appreciated and if i have to supply more info let me know i really want to get this going! thanks alot!!
 
But did you look at the [Boss ] on the right side of the engine block near the No 1 spark plug, the engine number is usually pretty close to the tractor serial number,unless it's a replacement motor, But we do know it's a 248 which was a 3 7/8 standard flat top piston, so now it's got some 4 in dome pistons that was the normal next step. they want to know the serial number because their was a different size bearing on the crankshaft, that was much latter, and there is a bushing to fit your piston pins to the newer/smaller wrist pins which i am sure you have those bushings in your rods now!! everything is fine the way it looks to me its a 1940. My oldest is a 1942, run like a new one yet.
 

thanks for the info! ive been waiting for a reply! the kit i was looking to buy was this one...http://www.yesterdaystractors.com/Farmall-M_Engine-Overhaul-Kit-Comprehensive-with-Stepped-Head-Pistons_EOK1155A.html....

im confused on what you mean by "boss"

just let me know if im going in the tight direction i really apreciate any information! and ill keep ya updated! this is my first tractor and hopfully it wont be the last!
 
A Boss is a raised part of a casting where they put information on, or used for other things, and when the item is being milled,, they mill that , and left intentionally higher for there own reasons. And the C 248 means Carbruated, because the diesel was also a 248 engine they need something to distinguish gas from a diesel
 
My other suggestion is take the air cleaner completly off and remove the oil cup and sit the part, with the steel wool etc in the parts washer. After that look from the top down and make sure that 50 year old dirt is out of there. Take a 16 inch long bolt and put some washer on the one end with some nuts and put your rag on the washers and shove it from the top down, get it nice and shiny in the air intake stack, Use AC 3116 spark plugs, and use 10w-30 or 15w-40 diesel oil, Its got the same amount of zinc as the old oil of 25 yrs ago.
 
Engine was changed sometime. If the sleeve OD and the block ID without sleeves measures close to 4.125 diameter use the 4 inch M pistons and thin wall sleeves that are used in M blocks for years. If it measures close to 4.250 ID without sleeves use super M pistons and sleeves.
Block cast # 6943 with a DJ suffix wasn't around in 1941.
Also the engine bearing size due to a crankshaft diameter change is the main reason for serial number breaks on the engine # for getting parts.
After all the years of changes its best to measure the crankshaft to see what bearing size is needed before purchase.
If no bearings included getting the correct valves is the only other concern.
 
5 7 J is the date code, the block was cast on May 7, 1940. That would be consistent with a tractor assembled in 1941 although May to December is a long time for a casting to sit around.
 
(quoted from post at 05:44:26 06/25/15) Could also be, and is most likely, 5-7-1963. He has a replacement


i will be takins a lit more measure ments by the sounds of it and ill be sure yo,post a lotof pictures! thanks fot all yhe inpuy and advise!
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top