Another Picture...

Question I would want to know. Did it leak coolant befor you opened it up? It would appear that if you had a GOOD head gasket seal, that that crack would not leak coolant out of the water jacket.

A better explanation from me is required. I purchased the block off eBay from a seller that clearly stated they did not know the status of the block, and had purchased it from an estate. They ran an antiques store, bought the estate for the antiques, and sold the block as-is. I paid a fair price, considering. I knew it could have issues, and bid accordingly. So, to answer your question, I don't know for sure if it was leaking into the combustion chamber, but I think it was. There are pock marks around the valves of the nearest cylinder to the crack. So I suspect, the head gasket wasn't holding back the water.

Best regards,

Ray

So how is the block, otherwise??

It took me a careful reading of what Zane posted to realize he was essentially making a clamp that would pull the crack closed to seal it, then use the block like that. Another way of saying, it is not much to worry about. You might not want to try the machining required. So JB weld might work just as well. The crack does not structurally compromise the block, it just is a potential water leak that you should be able to seal effectively.

In the location that it is, I do not think I would mess with trying to drill a hole at the end of the crack. The idea is to stop the crack from spreading, but it is not clear to me that you can be sure of exactly where the end is. Also it could be the end of the crack is angled so that the end inside is way under the top where it looks OK. If this were in the outside water jacket, it probably would not be angled.

The block is in great shape, otherwise. I think the block is compromised by the crack; the two nearest threaded holes for the head bolts are going to have lots of tension on them, and half their support is adrift, or unsupported because of the crack. (especially, the nearest threaded hole in the picture) By the way, only after looking at the photograph did I see the other crack between the furthest two water jacket holes (towards the top of the picture)

Here are a couple more pictures:

I do not see any problem with the strength of the material still available to hold the two head bolts. The one is very close to the cylinder wall, and that is where the strength will be, the other is even better, father away from the crack, AND between two cylinders where there are both walls for support.

I have my BS in Mechanical Engr., if that will make you feel better about my advice/analysis.

That is a water jacket hole - thankfully not a headbolt threaded hole.

Ray