A TECHNICAL ARTICLE FROM JUSTIN GREENWOOD
Here is an article from the New Jersey MG 'T' Register regarding a product that makes stitching a crack in a block relatively easy. A friend of mine in the Northwest MG 'T' Register tried this several years ago and so far it seems to be holding fine.
Cheers,
A STITCH IN TIME (Can save an XPAG)
By John Moon
Appearing in the Octagonia (Official Newsletter of the New Jersey MG ‘T’ Register)
When I inspected my 1953 MG TD this past Spring, I found that the water gallery under the manifold had a 6 inch crack along its length. We had a very cold winter and , apparently, the garage had gotten cold enough to freeze the water in the block. One freeze plug had moved, but failed to release the pressure.
I was afraid that I would have to pull the engine and replace the block - a prospect I didn't look forward to, since I only recently completed the restoration.
The obvious option was welding, but I quickly got an education about the properties of cast iron and the difficulties in welding it. Welding hardens cast iron along the area of the weld. Since cast iron is soft, it expands and contracts at a different rate from the weld, which is hard. The result is often another crack along the weld. It can be done, using special welding rods, but it requires an expert and still involves removing the engine. Then there are the epoxy options, but I didn't like the idea of being out on the road relying on an epoxy patch on my engine.
Then a friend asked if I had heard of "metal stitching". I hadn't. I researched it on the internet and was amazed by what I learned. Metal stitching is a technique of using special bolts made of a metal with properties similar to cast iron, so they expand and contract at a similar rate. The website had a presentation showing metal stitching being used on car engines, antique cast iron lamp posts, and basically anything made of cast iron. It can even be used to fix cracks in valve seats. The presentation went on the say that owners of high end antique cars like Dusenbergs, etc. used this technique on cracked engines because they are no replacement engine blocks to be had. The clincher for me was that this company had fixed the dome on the Capitol building in Washington, D.C. Most people aren't aware that the Capitol dome is made of cast iron. I figured if they could fix something that large, it should work on an XPAG engine. I contacted the Lock-N-Stitch company and talked to the president. He asked about the thickness of the cast iron and asked me to send a few pictures of the cracked area. Then he sent me an e-mail with his recommendations, which included stitching pins, a drill bit, a tap, a shoulder tap, and a sealer. Total cost was about $150. But I was fascinated by the process and figured part of the cost could be considered "education". The installation is relatively simple. They provided everything except the drill. They recommend using air powered tools, but I used a variable speed electric drill. The process is relatively simple. Drill a hole in the crack, use the shoulder tap to create a "shoulder" for the bolt to sit in, tap the hole for the bolt, then put some sealant on a stitching bolt and screw it into the hole. The stitching pins have a bolt head and a shoulder, so that when it is tightened, the head snaps off leaving the shoulder protruding from the block. Then the shoulder is ground down close to the surface of the block. The hole for the next stitching pin is drilled to overlap about a third of the first bolt, to lock it in place. Continue this way down the remainder of the crack. It takes about 5 bolts per inch. When I finished, I ground down the bolts down to the level of the block, and painted the repair. After painting, the repair was invisible.
I started the engine and ran it at normal speed and temperature, and inspected the repair at the end of the run. There were absolutely no leaks.
Keep metal stitching in mind next time you have a cracked block. It never hurts to have another option. I used a company called Lock-N-Stitch. There may be others. Their web site is www.locknstitch.com.
And as they say, “if I can do it, so can you.
|
is it?