I would not try to weld up the holes .nine times out of 10 u will warp the case..4 sleeves can be made in less than an hour.
if I had the case in hand I could (would ) make 4 sleeves for u to get u in the air,RAD.
I usually don't weld up the engine mounts unless they are broken. To fill up the holes, I would probably cut out the corners of the mounts to make it easier to weld up. i have worked on about 15 to 20 engines in one way or another to weld in a repair, and have never had a case warp or distort in any way. This includes putting the entire left side of the case and mount on a Brodak .40 (you could look through the hole and see the crank and rod inside,) and just saved a PA.61 for Mark Hughes that had all four corners of the mounts broken off in a crash that broke the crank shaft. He's put 5 or 6 bench runs on that engine to reseat everything and showed no issues, and he hopes to put it back in a model and fly it as soon as possible. I've done Foxes, OS, Super Tigre, all with success so far. You just can NOT get in a hurry when you do this and if I think it's needed, I do take extra measures to dissipate heat and back up areas that may fall through. On the Brodak.40, I turned a steel slug that was a slip fit into the crank case all the way to the front. That gave me something to build up metal on while I closed the hole. You preheat the case slowly to get the temp up, and you have to go slowly with the TIG torch with just enough juice to burn out all the oil from the casting in the area you need to add to. It will boil and bubble a bit, then just stop and wire brush it away, then get back at it again. When it's "clean" it will just stop, then brush once more and get back to work. All this takes a fair amount of time and can't be rushed, and that is one reason why I think the case don't distort. The structure of a case has all sorts of curves and angles to it to help hold it "square" and being aluminum, dissipates heat as fast as you can put it in. If you have a steel piece in place to act as a back up for any reason, that helps a lot also, I think. I have a pet theory that all of the heat cycles that an engine goes through in it's service life normalizes the case and relieves any stresses that may be in it that could cause it to warp when heated. I got started on all of this just to see if I could do it. If a case is screwed up enough that it can't be used, you can't screw it up any more than that, correct? So might as well take a crack at saving the engine. PA.61s don't grow on trees, ya know! I just applied the tricks of the trade I've learned over the years, and learned from any mistakes I've made. So far, I have not ruined a case yet. I do take the engines completely apart so as to not overheat any bearings and such. There isn't a engine case out there that is more flimsy than a Fox.35 stunt, and I have done several of those. It's not something I advertise, just do it for myself and friends and such. I lost the use of the welding equipment at work when I changed jobs 5 years ago, so this year decided to treat myself to one of the newer machines and try to get my hand back in it. I missed welding a LOT, no matter what it is! Everyone ought to know how to do it!
Type at you later,
Dan McEntee