simple to adjust...if the motor runs

idle motor with one valve cover off. best done at op temp if possible.

back off one rocker nut till the rocker taps loudly, then tighten it until the tapping just stops, then go about 1/2 turn more.

repeat 7 more times. turn off motor, replace cover, remove other cover and repeat.

you will have some oil mess, and check the level when you are done. the pic of the 'key ring' is the tool that helps stop the oil mess. Last time i did this (about a month ago) on an 80psi oil pressure motor, i had lost less that 4 oz of oil.

the non-running adjustment might be more accurarte, sure is more complicated, and easier to screw up.