My 1973 Jaguar XJ12L series II

It worked like a charm. Here we can see the offending article... and the cylinder head. Don't worry, I don't still have the beard !

Ooooh, barf ! However.... no hole in any piston, no evidence of broken rings. What had happened ?

Only after I had the thing back together did I realise that what was wrong was that the crankcase breather had become choked & had pressurised the case forcing oil past the valve stems into the cylinders.

Here's the head with cam in place.

And without.

Pretty rich running with some white deposits on the 6B cylinder exhaust valve.