Disclaimer - Non-rotorhead, but have more than a passing interest in the machines.
I found this in an article about the Bell 214ST in Helicopter World (Volume 5: Number 1: Jan-Mar 1986)
"During icing trials one of BCHL's 214s ingested a block of ice into an engine, clipping a compressor blade. The opposite blade was later clipped to balance, and that engine is still working at 106 per cent of its rated performance"
Note:BCHL = British Caledonian Helicopters.
I'm acutely aware that articles in the press may contain a bit of artistic licence and may not fully put the incident into context, however maybe someone like Speechless Two (or other ex-BCHL 214 bod) may have knowledge of the test that took place.