Here's a quick way to check for hydraulics. Remove the valve cover, and get a valve close to fully closed. Clamp a pair of vise grips on the rocker arm, and exert a firm, steady pressure toward the pushrod for a couple of minutes. If the lifter is hydraulic, the clearance between the rocker arm and the valve stem will slowly increase until there's about a 1/8" gap above the valve stem. As soon as the engine is re-started, the lifter will pump up to zero clearance again.
Jerry
