REbuilding M engine - change to Super M?

docmirror

Well-known Member
Standard M SN FBK2295xx. Would like to change to the Super M pistons, sleeves, etc.

1. Do I need to bore the block for the sleeves?

2. Is the pin dia the same?

3. Different valve sizes?

4. Different cam spec?

I know the carb is different, and the governor is set for 1600 max. Would like a few more ponies after rebuild.
 
Pistons and sleeves to make a M block 264 cubic inch was pretty well the standard rebuild for years on your engine and no boring required. Your M would be in the minority if still 248 size. For SM sleeves block needs bored to put in 281 cubic inch size pistons with sleeves.
Can get pistons with the same pin size. M and SM used the same rod end sizes.
Same valve size and very little difference in a gasoline head used on your M and a SM.
Original camshaft was the same on a M and SM. You can get better ones.
M carburetor can work good as the SM. Lots of those have changes made to fuel mixture over the years, depends the carburetors are the same basic design.
 
. Easiest way is to put the oversized 4 inch high dome pistons in with thin wall sleeves. This was pretty common practice with the m's when they were rebuilt. I am not sure if you can bore a standard M block out much more and still run sleeves
 
I did one 20 years ago. Had it bored out to accept
super m overbore sleeves. Another option would be
to just take the sleeves out and run on the block
with no sleeves. I think that would give you 4.125
bore too that would get you to 60-62 hp without
doing much else. As long as your head is a 8063 or
8574. A 450 head would be good for a couple more
 
Early M had a different crank and different
rods. I can't remember if they were
narrower or wider, but they are different.
 
Why not find you a good 264 block and drop the 281 kit in it( if you can still get one ). The kit comes with kit to rebuilt carb and distr,and template to
advance timing 22 degrees. Put a LP manifold on it and turn it up to 1,800 RPM and can get 76 HP out of it.
 
What D. Slater said is correct. The
early m cranks had a smaller diameter
crank on both rods and mains. But the
rods are the same, they used thicker
bearings to make up the difference.
When ordering bearings you must know
what crank you have. They didn't change
pin diameter until late in the 400
tractor and all 450's. They are 1 inch. The gas head is
casting number 8060, which could have
been on the m or sm. You really need to
verify these measurement yourself
because after all of the years and
amount these things have been apart,
you never know what's in there.
 
Yeah, I'm gonna hafta pull it apart and see what we find. It's not smoking that bad, was thinking of just rings and a hone. But - could be valve guides, and who knows what pistons, rods, crank is in there now.

I will get some advice from a local red engine guy too. I haven't worked on a IH engine before, so exp advice is going to help a lot. My plan is to just go up to hi CR pistons, and maybe run them in the un-sleeved bore if the cyl is round, and undamaged, but won't know until we get it down.
 
Is the tractor at a lack of power? Is it burning a noticeable amount of oil?

I once had a tractor (IH 300u) that burned so much oil it would foul out plugs. So much oil that I would have to add a quart for every 1 hour of operation time. I never figured out why, I just assumed get rid of that thing as the steering box was worn bad.

But if you are satisfied with the power of your tractor, and its not fouling plugs or having the need to add oil frequently then maybe its fine as is or a simple hone and rings would suffice.

But only you can decide. For reference though, my 1950 H had the motor rebuilt about 10 years ago. Runs great, but smokes if you let it sit on idle for a while then rev it up. Only smokes for a second then clears up. Good compression, runs fine, I don't add oil but once a year....
They are known to smoke a bit.
 
Also, if you re-ring it and don't have the head redone it will probably smoke just as bad or worse as the better sealing rings will pull oil down past the worn valves.
 

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