Case Nightmare And Ensuing Questions

[PEB]

I am doing a lower end rebuild and the machine shop that I took my cases to put a crack in one of the "shoulders" that a bearing fits into. It is the shift cam bearing on the igntion side near the bottom where the shoulder tapers. The crack runs the full width of the shoulder and stops at the outer wall of the case. The manager of the shop is talking about a small tig weld and perhaps some bearing compound as a solution, but I am very hesitant to take this route and I am thinking I should have him buy me new cases.

Anyone have any thoughts on the matter? My brother in law is a mechanical engineer and was wondering what the specific alloy of the cases is. He assumed they are cast and I told him I am pretty sure they are.

Please help,


Paul B

PS I will be borrowing my brothers wr450 for the next couple weeks and I pick up a new to me WRX tonight so I am suprisingly calm about this whole mess.

[LTRace]

Hi Paul,

The cases are cast, some of the thickest you will find these days. No telling exactly what alloy they are without extensive testing that probably won't matter in the end.

Considering the location you have described (a picture would be nice here, to actually see the location and extent of damage) it sounds like it should be no problem with a TIG weld and repair. Bearing fit and alignment may be your only issue and it sounds like this could be addressed easily.

These cases are really thick and sturdy (excessive in my opinion) and will hold up well to this repair. I have seen some pretty severe case "blowouts" from crank and transmission explosions that have faired very well for a long time without any issues in areas with more load/stress and far thinner wall thickness than the GasGas.

[GMP]

What did he do, put it in a big press and let it rip without proper support??

From what I hear the only potential problem with Tig on sand cast cases like these is the oil contamination. A good welder here at work told me sometimes its very difficult to get a clean weld, depending on the porosity, but is possible. If it were mine I wouldn't let the guy that broke it fix it. Call or email Ron at RB Designs and see if he can do the job or knows who can.

[widebear]

Gmp is right. It will be next to impossable to get a clean weld on that case material,even if the welder is a pro, not to mention any warpage issues ,due to a lack of pre heating. Even if you chemicaly clean the case ,there will still be tiny impurities in the material and it is very possible to end up with a pin hole that will weep oil.I know this because I built a custom turbo intake manifold for VR6,even on areas where virgin aluminum was used there was still pinholing, this was only found by pressure testing the unit, If your going to go that route I would highly recomend using some one to is a top notch pro in that field.It's to bad for the machine shop but they are going to have to ,suck it up on this one.