Another MD thread…

[1988case310]

I’m rebuilding my C291 and found myself thinking about my possible future MD restoration. Has anyone explored alternative parts and machining over sourcing rare parts?
Sleeves and pistons from a D361 are very close, would require the block to be bored out and decked, but would provide a steady source of parts aside from gaskets.
I have a gasser for parts, I’d like to tear down both together and verify all the differences between the blocks, sleeves, and pistons for reference. I’m wondering if the tractors aren’t used for heavy work, could gas parts be used provided machining is done to the block to accept them?
D361- 4.00” bore x 4.3?” OD, piston height is shorter by .080”
Even with the cost of machining, this could shave $2,000 from the cost of parts, that is, when you find the correct parts in stock.

Thoughts?

 

[Dieseltech]

The D361 direct injected piston bowls will SEVERELY lower the compression on the MD engine...

 

[caterpillar guy]

But would it be that much compared to the lost compression with the change over valves in there. Though if they were kept then it would be a net loss. IF not then it might be a wash. I'm asking not saying. The sleeves if I remember correctly are about as thin as sheet of paper almost. versus the thick MD sleeves. MD was 3-7/8 super was 4.0.Don't remember what the D-361 is. Might make more sense to just upgrade the engine to something newer. Like a little cummins or a small V/6or 8 just would change the torque a lot though with a V engine. Engine speed would also be an issue with 2200or so an MD would think it was flying in road gear.

 

[rustred]

But would it be that much compared to the lost compression with the change over valves in there. Though if they were kept then it would be a net loss. IF not then it might be a wash. I'm asking not saying. The sleeves if I remember correctly are about as thin as sheet of paper almost. versus the thick MD sleeves. MD was 3-7/8 super was 4.0.Don't remember what the D-361 is. Might make more sense to just upgrade the engine to something newer. Like a little cummins or a small V/6or 8 just would change the torque a lot though with a V engine. Engine speed would also be an issue with 2200or so an MD would think it was flying in road gear.

well no it wouldn't be as much but enough to make it not fire up, and blow white smoke. but you need all the compression you can get for a diesel. opening the gas chamber greatly reduces the compression by probably 250 lbs. to burn gas. to find any of them tractors with 3 7/8 sleeves now would be like hens teeth. most all are 4 inch and some 4 1/8. and by the time you pay for all that machine shop work your farther ahead to buy a set of sleeves and pistons for it.

 

[Dieseltech]

But would it be that much compared to the lost compression with the change over valves in there. Though if they were kept then it would be a net loss. IF not then it might be a wash. I'm asking not saying. The sleeves if I remember correctly are about as thin as sheet of paper almost. versus the thick MD sleeves. MD was 3-7/8 super was 4.0.Don't remember what the D-361 is. Might make more sense to just upgrade the engine to something newer. Like a little cummins or a small V/6or 8 just would change the torque a lot though with a V engine. Engine speed would also be an issue with 2200or so an MD would think it was flying in road gear.

It would be EXTREMELY LOW on the gas AND DIESEL SIDE, he will be taking out the original FLAT TOP pistons and installing pistons with a bowl instead.

 

[1988case310]

Boring the block runs $150-$200 here. Press fit (flangeless) sleeves can be had for cheap. The existing sleeves could be bored and honed for a tight press fit for new sleeves, and have the pistons turned down. It wouldn’t be enough that the rings couldn’t be gapped to fit. New sleeve kits are around $500 a hole or more, plus everything else that is astronomical on those engines, a grand saved is a grand earned

Understandably, they’re not worth restoring unless of sentimental value, which this one is. I have a couple 345s but really want to give the old diesel a chance.

 

[rustred]

ya but the rods, wrist pins, will need work . what the story on them. you say the pistons are .080 shorter, and where does the wrist pin bore line up ?and them pistons i dont think so. forget that money saving deal.

 

[Dieseltech]

ya but the rods, wrist pins, will need work . what the story on them. you say the pistons are .080 shorter, and where does the wrist pin bore line up ?and them pistons i dont think so. forget that money saving deal.

When it's done he could add three turbos and use a case of ether and MAYBE it would run...

 

[Gary Reif]

Boring the block runs $150-$200 here. Press fit (flangeless) sleeves can be had for cheap. The existing sleeves could be bored and honed for a tight press fit for new sleeves, and have the pistons turned down. It wouldn’t be enough that the rings couldn’t be gapped to fit. New sleeve kits are around $500 a hole or more, plus everything else that is astronomical on those engines, a grand saved is a grand earned

Understandably, they’re not worth restoring unless of sentimental value, which this one is. I have a couple 345s but really want to give the old diesel a chance.

Just wondering, what your plan would be as far as (turning down) the pistons. Factory finished pistons are not round they are cam ground or machined to be larger on the thrust sides. I would expect it would be hard to find a shop that still has a piston grinder. These are just some random thoughts.

 

[caterpillar guy]

Kind of an interesting discussion though as posed to my tractor is better than yours.

 

[showcrop]

A motor that I rebuilt a few days ago gave us piston sourcing problems but the machine shop that cleaned and inspected the parts has many sources and they were able to find some. The owner of the top parts company for these cars was amazed that they found them.

 

[Fritz Maurer]

But would it be that much compared to the lost compression with the change over valves in there. Though if they were kept then it would be a net loss. IF not then it might be a wash. I'm asking not saying. The sleeves if I remember correctly are about as thin as sheet of paper almost. versus the thick MD sleeves. MD was 3-7/8 super was 4.0.Don't remember what the D-361 is. Might make more sense to just upgrade the engine to something newer. Like a little cummins or a small V/6or 8 just would change the torque a lot though with a V engine. Engine speed would also be an issue with 2200or so an MD would think it was flying in road gear.

You've missed the point. The guy's endeavor is not to repower , but to try to find a way to make the existing engine rebuildable for anyone who wants to try it.

I have said for years that someone better learn how to weld these heads because the day is coming that these are all that are going to be left.

Nearly anyone can repower, but the guys with the will to fix these engines are the real thing.

 

[Dieseltech]

You've missed the point. The guy's endeavor is not to repower , but to try to find a way to make the existing engine rebuildable for anyone who wants to try it.

I have said for years that someone better learn how to weld these heads because the day is coming that these are all that are going to be left.

Nearly anyone can repower, but the guys with the will to fix these engines are the real thing.

I don't think I missed the point, but the D361 pistons are NOT going to work that he mentioned using.

 

[Fritz Maurer]

I don't think I missed the point, but the D361 pistons are NOT going to work that he mentioned using.

I never said they would. That's definitely an issue that needs to be addressed either by a piston contract with someone or turning semi-finished castings which not everyone has access to.

It's unclear to me if OP's intent is one- off custom parts, or making sleeve and piston groups available to the general public. Either way, this needs to be explored. Someone might come up with an idea too good to ignore.

 

[MeanGene1]

In the auto performance/race world, we have several places that make custom pistons to spec just about any way, bore, stroke (compression height, dished, flat top, domed, whatever. I have had some made for a non-stock bore size on a 428 Cobra Jet by finding an available ring size that was slightly oversize and then having pistons made to to match. One might be able to get a D361 type piston made as a flat top or dome, whatever you need