The butcher's bill is in.
All 16 valves bent:
Opened up the timing chain and was confused as everything looked great. instead of ripped chain and destroyed tensioner - they were both good, what happened was the locating pin in the VVT ring sheared, and the bolt had started to undo itself:
But cam follower still mint!
More drive belt found, the spindly thread middle left was jammed behind the cam wheel:
must have been rubbing behind the pulley before gaining entry:
I was a bit annoyed to find the head bolts are a special socket 10mm polydrive -ordered one, be here in 3 days - but left me stuck with head still attached - fortunately a T50 torx grips the head bolts just enough to remove them.
Pistons look OK -
No.1
No.2&3
No.4
Close up angle view of No.3:
After some brake cleaner and scotchbright, not even sure if there is even anything I can hone down & all the pistons come to the same height and damage is a lot less than I was expecting:
All 4 done:
So the upshot is I am happy to stick with the bottom end, getting a cheap second hand head, need to find another VVT ring and have a close review of the current lifters and followers.
Will speak to machine shop to get the upper cam pulley removed from the exhaust cam - it won't come off so the woodruff key has jammed + price out tank wash and possible valve guides.