Ok, I took the head off a mates Escos today, due to a suspect head gasket ( losing a small amount of water, & a misfire after cold start for a few seconds).

On removing the head, #2 & #3 combustion chambers have 1 small crack each, running from the spark plug hole to underneath the exhaust valve seats. #1 has a similar thing, but it is hairline, so needs further investigation.

All the exhaust valves are heavily coked, however the inlets are immaculate, which to me points to valve guides or stem seals on the exhaust side?

Has this caused the head to crack, due to the valves not being able to shed heat properly, or has the cracked head caused the valve coking from leaking oil?

The engine has 85k on it, with no reports of high oil or water consumption, and the head is 139mm, almost new ....

Can this be repaired in a safe manner?