3400 rebore opinions

Hi everyone,
I'll try to catch everyone up without writing a novel. I bought a 3400 with a FEL and Backhoe from a friend of a friend. He bought it in non running condition and from what I have heard, he is very knowledgeable when it comes to engine work, so I don't think he would have bought a piece of junk. Anyways, he had a heart attack and didn't have the energy to finish putting the motor together. So what I bought was a big puzzle. He had the head removed and it was rebuilt by a local shop and that was about as far as he got, never got it installed. He also had new rod bearings, rings and gaskets because he planned to replace it all.

Now I am trying to put the puzzle together. Since the motor is torn down this far, I also wanted to check the rod bearings and rings. I am in the process of pulling the oil pan off, but its a bigger job than I was expecting. Just out of curiosity, I measured the cylinder bores and it appears that the tractor has already been bored out to the maximum size. This is where I would like your opinions. If you were in my shoes, would you have the cylinders bored and sleeved or would you put the head back on and get it all back together to see if it runs as is? I have never had a block bored so I have no idea what a 3 cylinder gas block would cost to bore and sleeve. Any ideas? Of course that means 3 new pistons as well. I just hate to spend a ton of money gambling on a tractor that I have never heard run before. If its not too expensive to bore and sleeve it, I am tempted to have it done while I am in this far. Head is removed, oil pan will be off, front end will be almost off (if not completely) to drop the oil pan. Sounds like the only other major step if I wanted to bore and sleeve it would be separating the block from the transmission.

I will admit though, this is a little nerve racking for me because I have never done any work of this caliber. The most I have done is an intake manifold gasket on my pickup and I have torn down and rebuilt an atv motor. Nothing of this scale. I am a hands on type of guy and love to learn about this type of stuff. In a perfect world, if/when I get this running, the backhoe will be used to install a septic system or two and then the tractor/FEL will mainly be used around the farm, probably not very heavily used either. I am not shooting for a show quality tractor, just a good running piece of equipment. So what would you do if you were in my shoes?

Thanks for any opinions!

You really need to know where you are at. Are the bores in nice shape? No perforations from rust?
Are the new rings sized to fit the bore that now exists? Why would he buy new rings if he didn't plan to re-use the pistons? Is there a ring wear ridge in the cylinder? Is there taper in diameter from top to bottom?

If you can do the work without pulling the engine, that will save a lot of effort and avoid dangers.
I've always been told that you shouldn't rebuild a head without replacing the rings, too, or you'll have more oil consumption. If you were to put it back together, your main risk would be the labor and the wasted cost of a head gasket. Then you can check oil pressure, listen for knocks and watch for blow-by.

Not sure about the 3400s but I know the older 3 cylinder tractors were prone to cavitation when they got bored to +.040".

Is this gas or deisel? I just did mine (158 gasser) and found that the gas kit at .020 overbore was almost a grand as compared to the $400 deisel kits. Machining the block was $110 for aline bore, bore & hone. Crank needed turned and that was another $168. I did not need any sleeves.

This is just like rebuilding a really heavy atv motor....with 3 times the parts. You can do it, just take your time.

(quoted from post at 22:07:19 04/26/17) You really need to know where you are at. Are the bores in nice shape? No perforations from rust?
Are the new rings sized to fit the bore that now exists? Why would he buy new rings if he didn't plan to re-use the pistons? Is there a ring wear ridge in the cylinder? Is there taper in diameter from top to bottom?

If you can do the work without pulling the engine, that will save a lot of effort and avoid dangers.
I've always been told that you shouldn't rebuild a head without replacing the rings, too, or you'll have more oil consumption. If you were to put it back together, your main risk would be the labor and the wasted cost of a head gasket. Then you can check oil pressure, listen for knocks and watch for blow-by.

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The bores look like they are in nice shape, no pitting or any signs of rust that I see. The new rings are not the correct size for the current pistons. I have no idea why other than he assumed it was still original bore size. There is just the slightest of ridge, assuming it's not carbon buildup. Just barely enough to notice with a fingernail in some spots. No ridge at all in some spots as well. As far as taper, I don't know. I'll have to check on that.

(quoted from post at 07:39:34 04/27/17) Not sure about the 3400s but I know the older 3 cylinder tractors were prone to cavitation when they got bored to +.040".

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I've heard that the diesels are prone to cavitation but gassers are supposedly less prone. Mine is gas

(quoted from post at 17:38:27 04/27/17) Is this gas or deisel? I just did mine (158 gasser) and found that the gas kit at .020 overbore was almost a grand as compared to the $400 deisel kits. Machining the block was $110 for aline bore, bore & hone. Crank needed turned and that was another $168. I did not need any sleeves.

This is just like rebuilding a really heavy atv motor....with 3 times the parts. You can do it, just take your time.

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Thank you very much for the information. Mine is gas as well. I started checking prices last night on components and realized the same thing! A kit with 3 pistons and 3 sets of rings for a diesel is around $350. Just one piston alone for a gasser is almost $200! I couldn't believe it, almost makes me wish it was a diesel.

Was yours $110 per cylinder or for all three? Sleeves are about $30 each, so they wouldn't add too much cost. Thanks for your help!

The $110 was for all the machining on the block. If sleeves are available I wouldn't hesitate to go back down to stock. Around here (akron Ohio) it would've been $100 plus the cost of the 3 sleeves. Don't know what machine shop prices are around you.

I'd be tempted to put it back together with the pistons and rings left in place. Doesn't sound to me
that there is enough wear to warrant replacement. You may want to check the rod and main bearings in case there's a problem there.

(quoted from post at 06:49:21 04/28/17) The $110 was for all the machining on the block. If sleeves are available I wouldn't hesitate to go back down to stock. Around here (akron Ohio) it would've been $100 plus the cost of the 3 sleeves. Don't know what machine shop prices are around you.

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Thank you very much gears. The only other price I saw said 150-200 per hole, that seemed a little high to me. I am in rural kansas, so I imagine prices won't be too far off.

(quoted from post at 16:50:55 04/28/17) I'd be tempted to put it back together with the pistons and rings left in place. Doesn't sound to me
that there is enough wear to warrant replacement. You may want to check the rod and main bearings in case there's a problem there.

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Thanks cdmn. After seeing the price of pistons for the gas version, I am leaning towards trying it out as is. Like said above, all I risk doing it that way is my labor and a head gasket.

If you're going that route, yank your pistons lookat the rings. I bet they're almost wore through in spots, might be worth finding and file fitting a new set rather than a full rebuild. I know mine were wore down to 1/32" opposite the end gap!

How much taper? If less than .005 just rering.