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Cracked Block


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  • 4 months later...

with a cracked engine block could you just weld it for a temporary use until you get another engine?

For a short non structural crack like in a cooling jacket we used to fix them with a series of threaded plugs. One plug overlapped the last. but it's a bit hard to explain. Really kind of a lost art


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with a cracked engine block could you just weld it for a temporary use until you get another engine?

How bad/big is the crack?

Where is it on the engine?

Can you post a picture or two?

If it is just a hairline and on the water jacket side you MIGHT be able to get by with some JB weld.

If it is small and easy to get to you MIGHT be able to find a welding shop that has someone who can weld castiron.

And the last way and the hardest is to find a foundry who can heat the whole casting, weld it and the let it cool for a few days. This is REALLY the only way to do it but it cost the most and takes the most time and that is if you can evan find a shop that can do it.

The lock and stich method is the best way with out welding, but it is very time consuming and hard to do without being on a drill press, and thats after you pull the motor and find a press big enough to hold it.

If you go with JB weld you need to spend a lot of time prepairing the crack, grinding it out with a die grinder, then you want to drill out each end of the crack to keep it from growing. clean up the area and make sure you have no grease, rust, paint or scale in the area. Follow the instructions on the JB weld.

Also try to Google "repairing castiron" the information you get from there can help you decide which way to go.


1948 Mack Pumper
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I have been involved in the remanufactured engine sector for years. Believe me when I tell you that there are few times when a block or head is scrapped and only when it is not cost effective. We do this kind of repair quite often. A big part of our customer base are classic and muscle car engines. Last summer we had a inline 6 flathead Continential for a 1936 Mack jr that had crack block repair. The type of repair depends on the type of crack. A good professional welder with a correct welding rod can be a help in some cases. Safer welding is when the entire block is stripped and heated in a oven and welded. The repair that Joe Cummins mentions is done the most ( us old guys still have the art ) but anyone can learn. Many companies make the tools for this kind of repair. Go to the site Joe listed and go to REPAIR EXAMPLES, look at the pictures for the series 53 Cummins 5.9 engine block, that is the process. Basically you degrease the area of the crack, then you would use a MAGNAFLUXING process ( two magnets and iron dust ). this shows the complete crack from end to end. you then drill a small hole just beyond the end of the crack to keep it from spreading. The repair plugs come in many sizes and they are tapered and threaded. You drill the holes, ream them and tap them. we put locktight on the plug and thread it into the tapped hole. the plug generally will twist off flush when tightened, but not always in that case cut it. What you want is for every plug to overlap the next plug. This proceedure works well for cracks. In some cases JB Weld is good but if you can fine a product called MARINE-TEX this stuff is excellent for repairs. You can use this also to rebuild those cracked rims on the mack steering wheels and make them like new. Hey I use to restore cars. thats my two cents worth.


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  • 2 months later...

Are you saying I'm an old guy? :blink:

I'm not that old and I've used that method, you start at one end of the crack, drill the hole the size of the tapered screw(they were made out of cast iron),then use red loctite, screw it in tight and snap it off with pliers or an adjustable wrench.Then drill the next hole overlapping the first, continue till the crack is gone, grind flush and paint to keep from rusting.Tombstone

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  • 3 weeks later...

There used to be places to have it done- if it basically non structural- not to hard;ie-water jacket we had the a block fixed on a super A Farmall between the cylinder liners[the block was structural-the weld held] I believe the block was heated-if you have a small external freeze crack try sealant, know guys that have ran power units for years like that-Kevin

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