Freeze plug are actually a slang term.....technically they are core plugs used to get the sand out after casting the block..........sometimes the do pop when freezing since the nickname......but they are not intended as a freeze protect method. This is a very popular damage we see in boats that are not winterized correctly
When I had a cracked block I checked into Lock N' Stitch. Repair would have looked good, but they price at about $100/in. If that crack was 12 inches long, you'd be looking at 3 401 blocks at $400 you could have bought to replace with.
Wow, am I ever glad winters in South Western Alberta are fairly warm. Good wake up call to all. Check your antifreeze before winter. An oz (or a few gallons) of prevention is worth a pound of cure.
I had a block like that! It cracked in exactly the same way. The funny thing was, when I bought the car I had no idea that there was a problem; the engine ran beautifully, but it stunk. There was a lot of blow-by and the power wasn't there. So I figured it was just a bit tired and would benefit from an overhaul, which was something I could do. The previous owner had "detailed" the engine, so everything was a nice Detroit Diesel green under the hood and it didn't look bad. So when I decided it was time to rebuild it. I took the engine out, took the heads off, and then spun it over on the engine stand to take the bottom end out. On the driver's side, I noticed what looked like chewing gum wadded under the green paint. I took a screw driver and pried on it. It was Defcon, a lot of it. As it broke off, it exposed a foot-long stitch-welded crack with tributaries. I had a very expensive boat-anchor. I had already bought all the replacement parts, such as pistons, bearings, cam, etc., so I was already in too deep to quit. I took it to my machine shop and they told me to forget it, it was warped and leaking; - junk. I got lucky; they actually found a Buick Nailhead block in their back-40 that had been laying there for decades. It was sound and it became the basis of the current engine.
A long time ago, (1986-ish) at a jobsite I didn't spend too much time at... The manager sold an ancient Nailhead-engined Buick to one of his "friends". I was told to get it running. MASSIVE coolant leak. Couldn't pour water in the radiator fast enough to fill it. I crawl under the thing, and it looks just like yours, bigass crack from stem to stern, except with a heavy coating of sludge, grease, dirt, garf and garfelderfarb over the entire exterior of the engine. There was so much scuzz on the block it was hard, at first, to see the crack. So I tell my boss that the thing is totaled. He is NOT happy. I tell him that cast iron is hard to weld, he'd better know the best weldor on Earth (I didn't know about Lock-'n'-Stitch at that point) if he wants to save the block. He says "I am that guy" and dives under with the shop stick welder and whatever welding rods they had hanging around. About an hour later, he crawls out, defeated and filthy. Claims every time he struck an arc, he was flooded with black, molten slime. Yeah, that's what happens when you don't clean the scuzz off the metal before you heat it red-hot. The shop owned a fully-functional HOT WATER pressure washer, (had a propane heater, so the water came out about two degrees less than "steam") but of course he wouldn't use it. Too messy, too time-consuming. Idiot.
The crack in the OP is where frozen Nailheads almost always crack. I have seen a half-dozen blocks just like the one in the OP.
We have the same thing happen here in northern California. I have a v6 out by my shop, I did the same thing to it. Years ago my father in law crack a Ford 360 in Santa Rosa the same way. Yesterday I added anti freeze to my 401 so I could start it after it has sat for a long time. I no longer add just water with the plan of draining the engine, not worth it when I forget to let the water out. Anti freeze is cheap insurance...... Sorry about your block.....
Once you put anti-freeze in the block you need to run the engine so the anti-freeze & water can mix. IF you don't mix it the anti-freeze will not circulate & mix with the water & the block can crack.
The amazing thing to consider when things like this happen is that plain Grey cast iron has a tensile strength of 18,000 psi, and expanding frozen water overwhelms that! this is also a super reason to use Brass plugs on motors you care a lot about!
