Outer Limits 4x4 Board

hi all .
my problem is as follows .
i thort i had a liffter problem after replacing them i noticed the top off two
valves was chewed off to the colets .
would any one know why it has done this ?
could it have been a over time thing ?
or lake off services ie rocker ajustment ?
as i have only had this 4wd for a week i dont know service history .
it is a toyota hilux 3.8 chevy carbie motor .
also the valve seats look good and gides have no play in them .
any info would be great help .
as i dont want to put new valves in and they get chewed as well .
thank you ricky

have you checked the rockers for wear. i had this happen on a f65 , case hardening wore of the rockers them chewed of the valves.

27, Oil delivery prob or faulty valve tips.

hi
put all new valves in so its going again .
oil is runing to them fine so hope it was just old valve s .
now i have broke both engine mounts .
thanks for replys .
ricky