If I wanted to figure out what’s breaking a particular kind of piston aero engine (other than purely random failures), I’d set one up so that I could be sure that all cylinders are operating between about 40 and 50 degrees rich of peak on the lean curve, at high power and a relatively low cruise RPM.
That way I’d be giving the engine the toughest pounding that I could possibly give it. (Ssshhhhhh: Don’t tell yr right, but that’s ROP….)
I’d then apply time and observation.
I suspect most engine manufacturers are on top of that, and already perform similar tests.
It is probably something more obscure. Maybe something maintenance related, maybe something assembly related, maybe thermal cycle related. Someone hypothesized that it could be due to the mass of the hydraulic lifters because they are from a much larger engine.
The first thing we need to know is what are the common failures? Through bolts seems to be the main one being discussed.