The Stovebolt Site Forums The Shop Area Engine Shop Terrible news!

I've disassembled my 53 GMC 235 and it looked quite good on the inside. A rehone and clean up and should be good. So I began to clean the block and discovered to my dismay a cracked block! And it's a monster, almost the entire length of the water jacket. I was so excited that I was lucky to have a 235 but it wasn't meant to be this one. I don't think it's salvageable, it's terrible. NFG.
Anyone need a good boat anchor?
Should I compression test my spare 216 and use it instead? Runs ok but I'd like to drive this 1 ton often when I'm done.

There is a product used in the boat repair business called "Marine-Tex". It's one of the best sealers I've used, and before you scrap that block, try doing a thorough cleanup right down to bare metal (and then clean some more!) A drill motor with a wire wheel brush, or a cup brush on an angle grinder works for me. Spread on a layer of the Marine Tex about 1/4" thick and overlap the crack about an inch on each side. As it's curing, press a piece of 40 grit sandpaper onto the patch to mimic the surface roughness of the cast iron. The patch will almost disappear. The cooling system pressure for most stovebolt engines is usually low enough that a surface patch won't leak as long as the surface is prepped properly.
Jerry

way back in the day,when datsuns were spelled with a d instead n,my friend bought one with acrack between 1/2 cyl.we cleaned realgood filled with dental cement, rreinstall gasket/head torque to spects,,never had water in the oil again

Unless its somehow a numbered match for your frame or otherwise a rare/hard to find motor, I'd start looking for a replacement.

The epoxy repair would probably work, but as a daily driver your first tow home would wipe out any money you saved over buying a running motor.

Fox, I too had a very long crack. Mine was on the exterior. Not sure where yours is? The crack was about a foot long from the petcock to the center of the drivers side block. I used a product called locNstitch. It worked perfectly. Not s drop of water and you cannot see the repair after paint. Check the product out on YouTube. Good luck!

We used to repair cracked blocks with fairly good success, but we did our own machine work and parts were cheap. If we had a failure, we just lost time. With today's costs of everything, I wouldn't spend much money on a repaired block. There are lots of 235 blocks around that aren't cracked. I have one in a GMC that may well go for scrap pretty soon.

I think I might start to look for a replacement. I'd hate to finish the truck am then something go sideways on me. Plus, I think it would bug me knowing that it was cracked. I will look at the products you fellas suggested but may just opt out.
The crack is on the driver side and runs from the petcock to the #1 cylinder. She is a doozie.
Jerry, do you have a picture of your patch method? I'd like to see one.
Thanks guys!

A crack that big would scare me, and I am not easily scared when it comes to getting every last mile out of these old engines.
Carl

As Hotrod has said Marine Tex WORKS. Get the area very clean and put it on, wait a while before doing the sandpaper thing until the marinn tex is starting to set up and then use the sandpaper wet with water to ad the texture. Have Fun, Brian

I had this happen to me several years back. At the time, its a really catastrophic issue. Unless someone here gives you the name of a crack fixer, just resign yourself to needing a new block. The salvage yards in your area, this is true nationwide, (sorry Canada) have a network where you call one and they find you a new block no matter if they have to call several of their competitors to find it for you. Shop around, and each salvage yard will give you different prices depending on their business model. If you lived in central Kansas, I would sell you one pretty cheap. Even in Canada, don't pay more than a few hundred.

Fox, the problem isnt just that crack. If the engine was neglected to the point of having that crack, what else are you going to find, or worse, NOT find?

Since it's apart already, I agree on getting another block. Should not be hard to find a whole motor and get some spare accessories with it, or just a block. You will always worry about the fix. You may or may not have the same luck the others have had. There is movement, vibration, super heated steam and thermal cycling acting on the repair.

There are 6 very substantial vertical ribs in the side of the block looking from stem to stern on a 235. That kind of a crack is startling to me. Was it filled with water, frozen to -40 degrees Celsius/Fahrenheit (just showing off here), then dropped from 3 stories (What is the metric conversion for 3 stories?)
Anyway, sounds like Fox knows what he's going to do. All he needs is a big boat to go with his 235.
Carl

Just a good freeze with no antifreeze can produce that long crack on the lower rear driver's side.

I have a 235 with that clean and long crack sitting in my garage. It came to me cracked (and, unfortunately, is the "matching-number" H-M engine for a spare Hydra-Matic transmission).

I can live with that kind of crack. I put 25,000 miles on one without any issues. Mine cracked on a hot day when the original brass accordion-style t-stat decided to stick in the closed position, causing a major overheat and subsequent crack (I think). It needs to be mentioned that the water jacket was later found to be clogged up to the top of that crack with petrified dinosaur dung. Did that cause the crack? I don't know.
The OP was talking about a crack "almost the entire length of the water jacket." A different animal in my opinion.
Carl

"almost the entire length of the water jacket"

That would be like mine, I think.

I'll take a photo tomorrow and post it.

The engine ran fairly well before I tore it down. Of course it was a little gooey but nothing too bad. I took out the freeze plugs and the jacket was filled with crud too. So I pressure washed it, then scrubbed the block to see and found the crack along the bottom of jacket where the crud had accumulated.
The rest of this truck was in really good shape. It's too bad that it had a bad heart.

While I was searching for my 261, I looked at a 59 Chevy Viking grain truck. It had the 235 and I was disappointed because it wasn't a 261. The old farmer had parked it a couple years ago because the box and cab floors had rotted away. He said it ran like a top. Maybe I could score again! I think I'll call him. I could probably get it cheap.
Weird, I seem to be getting quite proficient at removing engines... As the parts shed begins to swell!

Years ago.. about 36 years, I purchased a 54 1/2 ton off a farmer that didnt want it around anymore for $75. It had a tree growing through it. I hauled it home and got a mechanic friend to help me get it started and running. It too had a crack all along the block like you are describing. I sold it several years later for $600 and the guy drove it away, after me putting about 4000 miles on it. But these days, no way would I spend any money at all on a rebuild or fix for that block. Too many good blocks out there and its just too costly for the machine work. It costs the exact same to machine a block that isnt cracked. Good luck Fox.. you will do whats right for YOU.. thats all that matters.