A buddy of mine didnt drain his water before freezing time got here, or didnt add antifreeze, and his block cracked slightly an inch below the head. About 3 inches long. Hes still running it and it doesnt leak too bad. I told him I didnt know if it was a good idea to keep running it or not. It probably has about 400 hp and he revs it up quite a bit.
Is this a crucial part of the block? Whats the worst that could happen? The block twists and breaks a crank?

 

The crack will continue to grow, and the cooling system won't be able to hold pressure so steam pockets could form and it'll run hot. If the crack isn't repairable (and maybe even if it is), that engine is trash.

 

I see. If the system cant hold pressure, then wouldnt the thermostat close up? Or never open? Its not running hot at the moment. The sender is in the head. If its not detrimental to the rotating assembly, maybe well just JB Weld it!

Mold it, Cut it, Grind it, JB Weld can do it!

 

The thermostat will behave just as it always has.

 

Tell him to buy that wonderful product called "antifreeze" that the rest of the world uses
He might be able to get a shop to heat it up with a torch and braze it shut. That part of the block doesn't move a whole lot, but there's still a good chance the crack will continue to move and it'll leak.
There are ways you can "pin" it. Google that method. I'm not so sure on how well it works.

 

On my 305, I had a leak around the temp sender and the thermo wouldnt open, motor ran hot as hell, and the fan wouldnt turn on. The fan sender was in the radiator. I fixed the leak and all was well....

I will look into ways to repair it, I've never welded cast iron. Dont think JB would be up to the task?

 

I doubt it.

Cast iron is nasty to weld. It has a major tendancy to crack. You'd want to tear the engine apart and clean it really well, v-grind it, drill the edges of the crack, and heat it up as much as possible. Then use a 90-99% nickel
rod. Then peen it right after, and keep it as warm as possible. It's still a crapshoot.

 

I'll qualify that then and say that the thermostat will behave as it always has, as long as he doesn't let so much coolant leak that it goes dry.

There's not much to lose by trying JB Weld at least. I wouldn't consider it a permanent solution. Before I'd try welding it, I'd fill it with plugs, but that's a tedious enough process that I'd just get another block. Maybe give it away to someone building an engine for a boat that doesn't have to care about a little leak.

 

Sounds terrible. No thank you. Blocks are a dime a dozen. Heck you even get a hundred bucks for them at the scrapyard. I'll try the JB weld and see what happens, thanks guys.
Oh, I wonder if it would be a good idea to stop-drill the crack. It would stop the crack, but maybe the hole would be large enough to push the JB out? And if that happened, it would be a big mess, and an instant strand.

 

If you don't drill the ends, it's probably going to grow.

This is the plug alternative I was referring to:

 

Drill,tapped, and cut off. I would think that would still leak coolant. We'd have to pull the motor to do that too. Ill just JB it and hope for the best, then a swift kick to the shin for not winterizing. It was a new motor and we werent sure if the cooling system was good enough, so we ran straight water for the break in. It never got changed. If the JB weld doesnt hold, well just change the block this fall.
Hey if we used all the exact same parts, it wouldnt need balanced again right?

Thanks for help guys!

Oh, and Apeiron, I see you have a dana 44? Is that with a four link or torque arm?

 

They don't leak, trust me. ;-)

My Dana 44 has a torque arm, it was one of the GMPP units.