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I got the call from the machine shop last week that my L134 is not a good candidate to start from. There is a crack along the #2 cylinder that creates "an uneven deck surface that can't be machined out". The shop said the block would have to be welded and even then they couldn't guarantee that I would not have head gasket leaks/issues. I heard $$$$.
It was not an MC block to begin with.

So the search begins for a good candidate close by. Ryan's book and my internet research has me looking for a 641087 cast block with 5 freeze plugs and 4 bolt holes on the bellhousing flange. I believe this is correct for MC25486. Please correct me if I am wrong.

Three questions:

Have any of you run into this situation and had the block repaired? How much did it cost?

What is the rhyme and reason to the casting #s after the block code? I can't find this information anywhere. As an example, the cracked block in Question is 641087-L-W11 A-NI-CR-N2.

Any 641087 blocks out there close to NW Montana? I'd be happy with a non-MC 641087 block from a CJ.

Wes, I'll fill out the survey when I get the block back. Thanks in advance for any info.............

All the letters and numbers after the 7 are foundry data and refer to drawing info, production info and metal content.

You are correct on an early 641087 casting for a factory class resto. Motor pool you can be more flexible. The late 10 bolt castings can be used with the early bell housing and plates but you will need to ground a bit off the right side for the timing window. Or you could just not use the timing window and use the later front crank pulley timing mark setup.

Check with Snake River 4x4 in Idaho.

I discovered my newly purchased M38 had a cracked block that the previous owner did not tell me about (with my cash in his pocket, why would he?). The crack went from the wall of #4 cylinder across a head stud hole to a coolant gallery. There was no fixing it. The problem is that the block is in places very thin with oil and coolant galleries running through it, like an egg shell. Yes, the exterior of a crack can be welded but the interior surfaces of a oil or coolant gallery can't be accessed - you can't get to them. Once started, a crack can radiate through the block due to stresses on the engine when it is running. So, once cracked, that's it unless the crack or break is in an easy to reach and non-critical area - each situation is going to be very different.

Sounds like both blocks may be candidates for cylinder sleeves.

Actually neither is a Good candidate for a sleeve. The first block has a deck to head sealing issue and the second block has a compromised stud hole neither of which can be solved with the installation of a sleeve.