The Stovebolt Site Forums The Shop Area Engine Shop What do you think about this crack?

Hey guys. First post here. I'm in the middle of rebuilding this old 250 and as I was starting to put the ancillaries on I noticed there's a crack that I believe is due to the torque on the head bolt right behind it. When I bought this engine I was told it was running when it was pulled out and I don't see any signs of any sort of leaks from this crack. Would you guys run it like this or do any sort of repair or just junk it?

Thanks
-Mag

Welcome to the 'Bolt Mag!

Have you removed the head to determine how far the crack extends? Without knowing more details on the existing condition of the engine, it may be cheaper to just acquire another 250, but really can't tell without more info.

Just judging from the picture, it looks like the crack may be through and exposed to the coolant passage, which would make it a must do to repair if you want to retain the engine. There are a number of ways, which I will leave to others more experienced in the methods and success or failure stories to discuss, but here again the question to ask is what is the value of the block?

Also just IMHO, but that crack would have been readily identifiable before the paint was applied. If whoever worked on it before you missed or ignored that issue, I'd be digging into the engine more to determine it's actual condition before trying to put it back to work.

Thanks for the reply.

It looks like the crack ends in the threads from the head bolt... I'm afraid if I take the head off the crack will worsen when I put it back on (possibly cracking all the way to the bottom, then expanding) and then I could get issues from the head gasket not sealing.
Right now I'm leaning on just running it and seeing what happens. Worst case, I'm out a few hours of time.... but I'm looking for some opinions on this from people who are more experienced with this than I am. If most people say I'm an idiot (they wouldn't be wrong) then I'll just junk it and start with a different one.

A crack in that position is not uncommon on a 250, and sometimes the same thing will be found on 230 engines. The block is a bit weak there, and even normal head bolt torque will sometimes result in a crack. Most experienced engine builders reduce the torque on that bolt by about 10%. It's way out on the corner, where a little less torque won't cause head warp or head gasket sealing problems. It almost always migrates into the head bolt thread. Since that one doesn't seem to have made its way to the water pump opening, it's probably fixable. Find the end of the crack, and stop-drill it to keep it from spreading further. Tap the hole for a machine screw- - - -8-32 or something similar. Then install a Heli-Coil thread insert into the head bolt hole. V-groove the crack and fill it with brass to prevent a coolant leak. Unfortunately, the above fix will require a teardown to the bare block, and a full rebuild.
Jerry

Jerry's fix might work with JBweld substituting for brazing the crack. I don't think it would get hot enough to affect the JBweld. You would have to get the crack area CLEAN to be sure the JBweld sticks.That would avoid a complete teardown.

If you're going to use an epoxy-type patch, on a scale of 1 to 10 quality-wise, JB Weld gets about a minus three rating. Devcon Epoxy Steel is a much better choice, at about 10 times the price. The only thing that beats brass for that kind of repair is nickel alloy arc welding. That opens up a 5 gallon size can of worms, however- - - -preheat, peen, post-heat, slow cool, and do a lot of machining afterwards. Another block would be less expensive.
Jerry

I had one just like that from over torque on the head bolt. It leaked coolant for a couple years till replaced the block. If you decide to try it, install a stud in the head bolt hole. Mine leaked no matter how I tried to seal it, I didn't try a stud. As the block warmed up, the cracked opened wider. It never ran coolant out, just always smelled of hot coolant and always had a drip on the bottom of the water pump. File it flat once the head is torqued down before installing the water pump, and set the block on end and drip Loc-tite into the crack or some other liquid that might run in to the crack and stay semi flexible. If you use a stud, be sure it threads to the bottom with thread locker, then use spacers to replace the head and torque the stud to pull it up into the threads while the thread locker dries.

If you try and weld it, the whole deck will need machined and possibly the bores since it will need preheated to weld. A stud threaded to the bottom may keep from pulling the corner clear off. I read somewhere that bolt gets 75 ft lbs where the others get 90, its been a while since I had a head off so the don't hold me to the 90 ft lbs. I took my block to a high tech weld shop and a machine shop, both said it was cheaper to replace then try and fix. I replaced it.

Ditto on the stud and threadlocker, but I'd also suggest drilling and tapping the thread a little deeper, to hopefully get past the crack. Since the block is on the ragged edge of being junk, that kind of repair doesn't have many downsides, if any.
Jerry

Hey Jerry, what's the reasoning behind drilling and tapping deeper? Is that for stress relief of the crack? Or to distribute the bolt torque over more threads? Or something else?

Hopefully, to get at least part of the threads of the stud below the area that's cracked. Since the stud is threaded into the block one time, and locked into place permanently with red LocTite, there won't be any torque load on the thread- - - -just a straight up pull from the nut on top of the stud.
Jerry

If you go this route, sneak up on the torque when you get to the nut, maybe go to 60 or 65 and stop. The engine has 8.0:1 compression or less so not a lot for the head gasket to hold.

This place offers a variety of ways to weld or repair cast iron that don't involve the aforementioned preheat, cool down, super expensive, just replace the whole thing rigormorale.. https://www.muggyweld.com/knowledge-video/brazing-cast-iron/

I know of an old guy, not sure if he's still around now, he had a cast iron welding business up north in this state that could make any broke cast iron part into a brand new looking casting, I was very impressed with a head he did for one of the bosses bulldozer back in the day.

I say never junk any of these parts, no one makes them anymore.

The correct way to weld cast iron is with actual little square sticks of cast iron, and lots of heat.

There is very little to weld to in that corner, 3/16" maybe from front to threaded hole, and then you need to keep the hole round and threads usable. You plan on welding the hole shut then drilling and threading, or you going to try and weld the crack and try to cut new threads in half the hole? You would be better off, cutting the corner off and welding a stud to the block and building up enough to face off for the water pump surface. The threaded hole is already compromised, it's no longer round.

I had one of these blocks exactly like this one. Everyone I spoke with said the whole block would need heated and the hole welded shut completely. Then the machine shop would rebore the crank holes, cam holes, cylinders, recut the deck, drill and tap the head bolt, and surface the water pump hole. I bought a whole running engine for less than the welder wanted.

Guys, it's time to apply Occam's razor here- - - - -we're not dealing with a museum piece like a Duesenberg or something similar. If the block can't be made serviceable with a Heli-Coil and some low temperature bronze welding rod, scrap it and find another one!
Jerry