Boring out Farmall M Engine Block

JBlavl

Member
I'm in the process of rebuilding the engine on my Farmall M and I ordered a complete engine kit from Yesterday Tractor. Everything looks good. I went to drop the new sleeves in the block and they are loosey goosey. I measured the bore in the block and it is 4.25" The sleeve I pulled out has a piston size of 4.125" and the new one from the kit is 4.00". I bought the oversize kit knowing it is a direct drop in replacement. But based on the numbers it appears someone along the line had rebuilt this engine and had it bored out to accept Super M sleeves and pistons. I know its a 1939 M block. Tag on clutch housing and serial number stamped on block match. I guess my question is how common of a thing is it to see a bored out M block and if I order a Super M kit will the sleeves and pistons be the only thing different from the M kit? Look forward to the replies and thanks in advance.
 
This is probably not what you want to hear, but I
had a similar problem. I am not a mechanic so I was
having the work done on one of my M's at the IH
dealer. The engine that was in the tractor had been
re-bored and had no sleeves. It was WAY more
expensive to fix that engine than to buy another one
from Bates Co. Hope this helps with your decision.
Ellis
 
you need to exchange that kit for a sm or 400 kit with 4 1/8 pistons. I have a 400 with a 248 block that was bored out to fit the larger sleeves which sounds like what you have. It has 400 sleeves and pistons in the 248.
 
There's a big-big difference between boring the block for 400 sleeves and pistons, and running pistons directly in the block.

All you need to get that numbers-matching 1939 M up and running is the right rebuild kit. It would make no sense to junk the block for this or go to great lengths to return it to "stock."
 
Just keep your stock block with the BIGGER bore
sleeves and pistons."Numbers matching" block is
cool!!! Who cares about the "Innards" anyway?
It is the SAME in the muscle car world. If the
BLOCK matches,NO ONE cares about what happened
inside the engine!!!

Just get you a new sleeve and piston kit to match
the block you have now.

I WOULD NOT order parts for a block until I knew
its dimensions anyway!

Check your bearing sizes as well.
 
Thanks guys that's about what I was thinking. Already sent the M sleeves, pistons, and rings back (waiting for credit on those), and have the Super M kit on the way. I have a feeling I am going to take a hosing on exchanging the parts but guess it's payment for not measuring before hand. I never would have thought boring out a block to accept Super M sleeves was common practice. Oh well live and learn.
 

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