[KetyElly]

According to what I can find on that engine it uses DOHV camshaft setup and they use valve adjusting shims either over the bucket or under the bucket design. It may may be that shims are either worn or the valves are worn and thicker shims are needed.

Now take this a grain of salt as I have repaired a DOHV engine valve train yet.

DOHV = Dual Over Head Valve (other words two camsshaft with one for intake valve and the other for the exhaust valves)