First- - - - -remove the side cover over the lifters and find out for certain whether or not they're hydraulic. A hydraulic lifter has two pieces, with the inner plunger that the pushrod contacts able to move down with a steady, constant pressure applied to it. Find a valve that's completely closed (distributor rotor pointing to the spark plug wire) and apply a steady, constant pressure to the rocker arm with a pry bar like you're trying to force the pushrod down into the lifter. If it's hydraulic, after a couple of minutes of steady pressure the gap between the rocker arm and the valve stem will be 1/8" or more due to the lifter collapsing. If the gap doesn't change, you do not have hydraulic lifters. Adjust them to the solid lifter clearance specifications.
To do the hydraulic lifter adjustment, point the distributor rotor to a plug wire, and loosen both rocker arm adjusters on that cylinder until there's visible slack between the rocker tip and the valve stem. Finger-tighten the adjuster until there's no slack, and tighten another 3/4-1 turn. Tighten the lock nut. Adjust both rockers that way. Move the distributor to the next spark plug wire and do the same thing. Ditto for the complete firing order. Wait a few minutes before starting the engine to allow the lifters to bleed down to the correct position.
Now the valves are adjusted- - - - -bolt the valve cover on and go tinker with something else!
Jerry
