Gents (and Ladies?),
Why would a valve stem snap?
I rebuilt my old CF1 T/Spark 1.8 after a water pump failure wrecked all the valves.
The crank bearing shells were all fine (no marks at all) and the pistons showed only the faintest of marks so it must have been a gentle one.
Head was rebuilt professionally (all new valves and seats) and I also fitted 8 new buckets (all on the Inlet side) since a couple of the buckets (both from the exhaust side) were looking a bit ropey - from wear rather than trauma. I put the best 8 of the remaining 14 buckets on the exhaust side.
When re-assembled, the motor was running sweet. Probably as good as a TS can run, if I say so myself.
Sadly less than 200 miles later the beast just died on me in a cloud of oil smoke.
I have just removed the head. The head of one of the inlet valves (no. 2 cylinder) looks like it snapped off (about 8mm up the shaft) and then got smacked into the piston, stem "stub" first, putting a hole in it. Then it go wedged in the valve port and generally knackered the combustion chamber. The big plug was not a pretty sight.
I'm mystified what went wrong. The valves were all new (they had to have been) and even if they got walloped again, they would surely have bent, rather than snapped off? On the Top side (rockers) everything looks okay. No issues at all.
The Motore somehow did still run on 15 valves and a holed piston...
but perhaps "a bit lumpy".
The wreckage in the chamber is not pretty..