Magnesium casting repair question

[Mike Ahrens]

Well, the next time somebody starts a thread about "What's the stupidest stuff that you've done in racing", I'll have something new. I was repairing some stripped threaded holes in the oil tank / bell housing main casting on my SE-3. Plan was to drill the holes out a little, tap them oversize, and put in a steel insert. All that worked great, except the hole broke out where it shouldn't have, and now I have a significant leak. The hole's not real big, but it's obviously gotta get fixed. The question is, how? Can magnesium be welded? Is there some sort of an epoxy solution?

[Frank C]

Mike:
When I had a little problem with a snap ring groove in an aluminum upright (too big a press in the hands of an idiot, yours truly), a fabricator I contacted (he has an impecable reputation but I am reluctant to give second-hand endorsements) told me to send it to J&J Racing outside Philadelphia. They did a nice job promptly and reasonably. Their web site has a section on aluminum and magnesium casting repair:
Casting Repairs
I would contact them. E-mail me if you want a little more advice.
- Frank C
chambersfw at yahoo dot com

[R Silver]

Mike, I put a new oil tank in my VD a few years ago and one of the pick up threads came tapped through. I put thread sealant on it (red high temp I think) and have not had a problem since. You might try that first since there is not a lot of pressure in the gear box. Some of the screws on the bottom are tap through by design and dont seem to leak. Worse case, J&J are probably the best around for magnesium and you are pretty close. I have had them do a few magnesium repairs over the years and they are quite good, but I would try sealant first.

-Rick

[stonebridge20]

If you broke into the sump........Do yourself a BIG favor and clean the sump VERY well. My first year racing, I drilled out one of the front oil pan bolt holes (the one that goes into the front cover) and broke through. A chip of aluminium somehow got to the oil pump and locked it up and broke the cam at the oil pump drive gear. As far as sealing up leaks in a pinch.....Go to the local boat store and get something called Marinetex. This stuff is magic! I watched a friend "glue" a chunk (2''X 3'') of 711 block back in the side of a slightly used race engine and race it that way for 2 years!

Good luck, Mike

[Chester Carter]

Have had some experience and more luck than I am normally afforded patching damaged race bits. There are a couple of must do's to seal magnesium effectively. #1 clean both sides of the material completely with brake kleen, or other non residue cleaner that will remove all traces of oil. #2 heat the material, even if it is the entire gearbox with a space heater that will heat it untill it is too hot to hold your hand on. You may have to reclean several times due to oil magically reappearing at the damaged area. I normally use "J&B weld" since it seems to be available everywhere. I favor the regular and not the "5 minute" stuff. even though I carry it along on the trailor. Once the "J&B weld" is applied you may have to rotate the material to keep it on the damaged place. When warm it flows quite nicely and will enter the cracked area readily. it may even be necessary to build a little dam to contain the epoxy untill it cools. Let it cool normally and the epoxy will have cured as smooth as a baby's bottom. If neccessary to remachine try using drills with brad points or use a milling tool. this will prevent the normal "wedging" or spreading of the alloy that leads to cracking such as you have encountered. this procedure works equally as well with cast iron such as when opening up the oil galleys to cross oil the engine. We have been using a 1600 engine for over 15 years with a 1" crack into the main oil galley that has over 90lbs of pressure cold on it. Same procedure used successfully.
P.S. never do this on something structrual. Chet Carter SF region.

[Mike Ahrens]

Thanks, guys.

A litle more detail on the hole....The tapped holes I was repairing were the holes that are used to mount the plate that is on the bottom of the casting. I have been removing that plate to change the oil, so the screws were in and out a lot, and the threads were tired. BTW I've made a new plate with a drain plug in the middle, so I won't have to do that anymore. Anyway, when I drilled the two holes that are closer to the engine, the holes broke through the side wall of the casting, which makes the leak path into the bell housing area of the assembly. At first I thought it was a rear main seal, but the oil was on the wrong side of the flywheel. Oddly enough, it didn't leak until I had the car on the track. When I put everything back together and ran the car in my driveway, no leak. After a weekend bouncing around Nelson, it leaked big time. It's not structural, so I'll probably try some sort of a patch, but I need to finish taking it apart before I make the call for sure.

Thanks again for the input.

[LolaT440]

I had some work done by John Rogers Racing in CT. Extremely good.

But as Mike20 mentioned, Marinetex is great. In Highschool, 1980's, I cracked the exhaust manifold on my fathers vette. 350-350. That Marinetex is still sealing that crack.

[Mike Ahrens]

In the end I patched the hole with a two part epoxy. Worked great, and easy to do. Thanks for all the input.