We've had a rash of casting problems with 3W-106s around here (3 of 5 at our field this year). After the engine is fired up, you can see the case oozing goo from the imperfection. One guy fixed his by applying JB weld (runs fine). The next send his back and had the case replaced, then sold it and bought a DA. The third engine has been parked with a disgusted owner.

Another member of our club had the case fail in flight, as in it broke apart, on a 3W-150.

Mine is one of the non-leaking 106s and runs fine, I feel lucky!