When our Mild-Mannered Mauler 440 first met the dyno, deep within its gut spun a radically fast flat-tappet combo, measuring 231-degrees at .050-inch lift, and shoving the valves to .600-inch lift with a custom set of Harland Sharpe 1.7:1 rockers. Hydraulic instability in the lifters plagued that test; the mechanisms just couldn't cope with combination of intensely rapid motion and the inherent valvetrain inertia. A test with solid flat tappets on the same cam proved that there are difficult to overcome limits here. Peak torque seen with the hydraulic lifters came in at 560 lb-ft. at 5,000 rpm. Our best horsepower was found when solid lifters were substituted and lashed at .004 inch for testing purposes, recording 607 hp at 6,000 rpm. This is the rpm level at which the hydraulics were in control chaos.