Variable Pitch Props
This failure was allegedly caused by a previous operator over stressing the crank by turning up (coarse) the variable pitch prop and raising the BMEP beyond limits. (time trial racing) The subsequent buyer then suffered an engine failure when the crank failed and a forced landing was unsuccessful. I have seen the photos of the crank in the report to the coroner (original copy by the author) and one of the recommendations of the coroner's report was that all RAA aircraft running a variable prop must be fitted with manifold pressure gauges.
Never seen a failure like it before or since