First get a replacement valve cover gasket. Don’t skimp get a good one. Remove spark plug wires, blow out plug holes and remove spark plugs. Check the gap on them them put them back in their respective holes but don’t thread them; just leave them loose. This allows compression to release and makes it possible to turn the motor. Remove intake manifold brace and vent tube from valve cover. Take off nuts in reverse order of Bentley tightening order to prevent warping. Lift off cover and remove gasket. Make sure all gasket material is off of the head.
To adjust valves, start with cylinder 1. With trans in neutral take a long 21 or 22 (?) and turn Jesus nut on front of crank until cam lobes on cyl 1 both point down and the rocker arms are at the lowest point on the cam shaft. Slide the feeler gauge under the rocker arm where it meets the valve. Rock the rocker arm (ha) back and forth. It should not move. If it does, loosed the 10mm bolt on the rocker arm eccentric and rotate the eccentric with a 2.5 mm Allen wrench until it touches the feeler gauge. Tighted the bolt slightly and check again. The feeler gauge should slide in and out with just a hint of resistance ad the rocker arm should not rock until the gauge is removed. Tighten bolt firmly. Repeat for the other cyl 1 valve and then do 5,3,6,2,4 by turning Jesus nut towards passenger side (I think).
Put gasket on and tighten nuts according to Bentley order and torque (don’t forget plug wire rail). Tighten plugs to torque, fasten vent and brace to cover, put on plug wires, wash hands, open beer and enjoy your quiet motor.