273 mech rocker problem
next time you are in there clean off the valve tips with brake cleaner colour them in with sharpie and see where the contact patch is ideally direct across the middle of the tip
but hey anywhere within the middle 60% would do if its rolling off the front or rear edge of the tip at 1 extereme or the other it will wear/mushroom the tip and wear the valve guides......eventually...
if you have got this far with no issues its probably not doing that
Dave