Cracked block - fixable?

torch

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Jun 10, 2016
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Nevermind JB Weld or similar on the outside. Get a can of CRC Block Seal. Unlike most cooling system sealants, this stuff actually works long term. The gotcha is the system has to be completely flushed of anti-freeze before adding the product. Then completely flushed after treatment before replacing with anti-freeze. But if you follow the directions religiously it works well.
 

Lil Foot

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My JB weld story, posted previously:

"Years ago I was at a drag strip watching a gorgeous blonde woman run a long gas dragster in the 8-9 sec range. Went to her pit to talk to her and she showed us the car. It had a built 327, with no radiator, and had to be cooled between passes. I noticed a repair on both sides of the block, about 8-10" long, below the deck & above the block drain. Her husband said they found the car in a storage facility in Colorado, where it had been stored with no anti freeze, splitting the block. They bought the car for $400, ground out the cracks to a "vee", cleaned everything, and troweled in JB Weld. The car had been running 20 years on that repair. That was what initially sold me on JB Weld. Good stuff."

That repair was on a wide flat area, with little to no stresses, and probably less heat and less rapid temperature swings than the original posters problem.

YMMV.
 

D2Cat

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If I were doing the JB repair I would take a 16P nail and bend the end 90 deg about half inch from the point. Use that to scrape the crack just to clean it out a bit. Then when applying the JB have a piece of duct tape ready to put over the whole thing. This keeps the JB from flowing out/down the cracked area.

I did a similar repair on a JD 350 crawler block. Had about a 4" horizontal crack below the freeze plug. Cleaned it, applied JB and covered with tap. Never messed with it for about a week. As far as I know it was running 10 years later.
 
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Runs With Scissors

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To be successful using JB Weld, I think you need to start by getting a can full of gasoline and pressurizing it ……………………..:oops::eek::cautious:





EDIT: I’m also in the “Don’t waste your time” camp…………..
 

hedgerow

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Jan 2, 2015
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Anybody remember waterglass from the drugstore for fixing large cracks?
Good Luck!
I used it on a old JD model G forty plus years ago for a cracked head issue. It was still holding twenty years later when I sold the tractor. I told the guy what I had done twenty years before. He didn't care as the tractor was going to be used for tractor pulling and was getting a different engine.
 
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Vanguard08

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Jan 6, 2026
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I don't really know what to expect so I won't be getting my hopes up but like someone else mentioned, it's a cheap test so I figure no harm no foul.

I took some more pictures so you can better place the crack. I whiped it down, used vinegar to clean off any residue and rust, and then used a steel wheel Dremal brush to get a better clean all over it, then I used a torch to burn off anything around it. I did this a few times trying to get it as clean as I could.

Here's a few pictures:

Here's a better picture of the crack after I whiped it down with some vinegar:

1768160877980.png


It does come from underneath though so it's a bit worse than it looks. Not a lot... but enough that it's gonna count.

Here's a zoomed out view I took after I removed the fuel tank:

1768160909839.png


Here's a picture after a bit of cleaning, you can start to see it more clearly:

1768160978591.png




And... here's a picture of my probably laughable attempt to patch this thing up. Not the prettiest but I did try to get a nice even glob spread all around the area:

1768161218295.png



I'll let that sit for a day or two and then we'll see what's what.
 
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North Idaho Wolfman

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That's just a head crack.
aand it's more than likely only external.
If you pull the head you could get it fixed properly and never have an issue again.
 
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