Cases are going to crack. The VW engine was only intended to run down the road at less than 50% power most of the time. In an aircraft, you ask a lot more of it than it was ever designed to do. Even Continental and Lycoming have cases crack occasionally. The Lyc O-320 I overhauled for my Cub had to have one case half welded and it only had 1855 hours total time since new. It happens due to stresses on the case and possibly imperfections in the casting.
With the VW case, it's unlikely that the case was checked for cracks with dye penetrant before the engine was built, so it is possible that there was already a crack there, either from previous use of the engine, or from a defect in the casting. In either case, things like a poorly balanced engine will promote this type of failure, but may not necessarily be the cause. Jeff Scott Los Alamos, NM ----- Original Message ----- here is the link to pics http://s887.photobucket.com/albums/ac72/pjb0150/ 1835 vw about 300hrs no prop strike yet this happens what about weight of prop what about yawing with high revs on what could have caused this phill
