Karl, if you can make the gap at the valve stem change by pushing down on the pushrod side of the rocker arm, it's almost a certainty that you're working with hydraulic lifters. The gap simply cannot change with solids. With both valves closed and the piston near the top of the compression stroke, apply some steady pressure on the pushrod end of the rocker with a long screwdriver or a pry bar. Within a minute or two, the gap at the valve should increase slowly until it bottoms out at about 2 MM or so. That is caused by the oil in the lifter being displaced and the lifter plunger bottoming out. It will refill after a couple of minutes of running time.
The best way to adjust the lifters is to get each cylinder to top dead center with the engine stopped, take the free play out of the rocker with the adjusting screw, and continue to tighten the adjusting screw 3/4-1 1/2 turns further to preload the lifter. Don't worry about forcing the valve off its seat- - - -the lifter will bleed down and allow the valve to close within a minute or two. Continue to adjust all 6 cylinders that way. A good way to determine when a cylinder is ready to adjust the valves is to align the distributor rotor with the spark plug tower in the cap for the cylinder you're about to adjust.
Jerry
