Quite possible.

A few interesting points to note.

It only appears to be intake valves. I cant see the same cracking on any of the exhausts.

All 8 intake valves had the cracks. But 4 from one head were alot worse than the 4 from the other head.

I dont know if it affects things. But my valve guides were not replaced when the valves were fitted.

I donk know for sure, But I dont think the seats were cut, or even lapped at the time of fitting the valves?

There are no piston to valve witness marks on any of the pistons. EXCEPT the piston from the cylinder that had the rod bearing failure. And im certain this would be as a direct result of the rod bearing being munched, alloying the piston to touch one of the valves. Only one valve touched. And all 7 other intak valve recess in the pistons appear perfect.

The car did from time to time bash limiter.

__________________
Doing it for all the wagons out there