Valve guide boss cracked

As long as it doesn't migrate... Shorter guides wear faster because there is less area to deal with side loading imposed by the rubbing action of the rockers. Roller rockers will do this as well, but maybe not as fast? At the risk of bench racing again (winter is killing me!) I am skeptical of how much value a rollerized rocker really has. I am not as wildly optimistic about the outcome as the aftermarket would have us to believe about roller rockers, although I would use them myself. I believe most gains in rockers are from an improvement in strength/flex resistance and harmonics. There are people a whole lot more experienced than I on this topic on here though, and many new factory engines use rollers, but the rocker anges/etc. are engineered with this in mind ahead of time. In this case it's usually not just an add on/improvement to an existing design.