In my experience with large radial engines (CurtisWright R3350 turbocompound series, P&W R2800CB series), the Bifler pendulem dampers (crankshaft counterweights) are the problem, with overspeeds.
These counterweights are there to dampen torsional vibrations, and during gross overspeeds (sometimes not so gross as well) these dampers can become 'out of phase' with the rotational forces, causing bent/fractured con rods.
Oftentimes, the master rod bearing is also damaged, which leads to abrupt engine failure...expensive.
Now having said this, my experience with these large radial engines was all too brief (the chief pilot of one operator I was destined for, tried a short field landing with a 1649A Constellation, which tore the gear off about a week before my type rating ride...damn), so I stand to be corrected by those with better ideas.
Additional information can be obtained from the website..
www.enginehistory.org