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Help repairing a cracked block


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OK, I finally got my Fast Four Engine up an running only to discover about a 1" crack in the block. The crack is at the front of the engine and very easy to get at. Does anyone have a suggestion for repairing the crack? I would like to not have to remove and tear down the engine if at all possible, since I just finished getting it all together, painted etc. My first thought was to try and repair the crack by drilling small holes at each end (so it doesn't continue cracking) and then using JB weld to try and seal it. It's not a large crack, but water does seep from it... Any suggestions are appreciated. - Jim

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Okay, after you drill it, "V" it, and fill it (be it with JB or other materials), you should be able to shape it (with a grinder or sander) and then detail it.

I find a “rust descaler” (air tool with a lot of metal rods that vibrate) or an engraving tool can assist you in putting in the porus "cast" look to your repair and engine paint would make the repair practically undetectable.

Best of luck,

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There's an 80 year old machinist here in Oklahoma City that uses a different method of repairing cracked blocks. He drills and taps a hole on the end of the crack and the puts a tapered screw plug in it. Then does it again, overlapping the first one and continueing unil the entie crack is addressed. He also uses some kind of sealer on the tapered screws. The last time I heard of him doing this was on a big diesel engine in some sort of off road prime mover. I have also read about it in a magazines years ago. You might want to check around where you live for an older machinist in an older established automotive machine shop and see if some body still remembers how. Another suggestion would be to find a good welder. There are some newer welding materials out there now that are compatible with cast iron. I haad an exhaust manifold on my '38 welded about 10 years ago. The guy heated it in an oven before he welded it. Have had no problems with it since. walt Bower

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The plug system involves using 1/8" pipe plugs. You need a 1/8" pipe tap, the correct tap drill, a 3/8" drill, a small hand grinder, a wrench and a supply of pipe plugs and thread sealer.

The procedure is to drill the first hole centred at the left end of the crack, tap the hole and tighten in the pipe plug liberally coated with thread sealer (do not overtighten as you may cause a new problem). Grind the plug flat, Drill the next hole centred at the intersection of the pipe plug and the crack, tighten in the next plug, grind flat, and repeat until the crack is completely repaired. This system is called "stitching" and has the advantage of being a cold repair as well as being absolutely permanent. I have done many, and it is a sure-fire solution although labour and time intensive.

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I would not be comfortable with the concept of using tapered pins. A tapered pin would have only one sealing surface, essentially a line around it where it forms an interference fit with the block - not much sealing surface. In contrast, a pipe plug is designed to seal against pressurised liquid and has a great deal more sealing surface. In addition, the pins would have to be driven in, and I don't like the idea of repeated impact on an already weakened surface.

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Brian, I've heard of useing pipe plugs, which are a tapered thread. But the stitching I'm talking about uses smooth straight pins, like 5/16 or 3/8 diameter. The hole is drilled centered on the crack,and reamed to about .001 press fit, pin is gooped up with your favorite mixture of sealant and pressed in place. The next pin overlaps the first, locking the first in place. A little differant method, but same result. I agree with not wanting to put extra pressure on an already weak area. I personally would use either method over welding any day.

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