The Tests
Here's how the 572 measured up in stock trim:
Horsepower: 620 @ 5,500 rpm
Torque: 650 lb-ft @ 4,500 rpm
Compression ratio: 9.6:1
Block: New Sportsman tall-deck Bow Tie Gen VI, 10.200-inch deck height
Bore: 4.560 inches
Stroke: 4.375 inches
Crankshaft: Forged steel
Camshaft: Hydraulic roller
Valve lift: 0.632/0.632 inch
Duration at 0.050: 254/264 I/E
Cylinder heads: Aluminum, rectangular port
Intake valves: 2.25-inch stainless steel
Exhaust valves: 1.88-inch stainless steel
Rocker arms: Aluminum roller rockers, 1.7:1 ratio
Intake manifold: Aluminum tall-deck single-plane
Carburetor: 850-cfm Barry Grant
Ignition: MSD HEI @ 36 degrees total
Test 1 - Our ZZ572 as delivered from GMPP produced 649 lb-ft of torque at 4,800 rpm and 648 hp at 5,700 rpm.
Exhaust: 2-inch headers, 3-inch Flowmaster dual exhaust with H-pipe and Flowmaster Super 40 mufflers.
Test 2 - We broadened the torque curve by replacing the open-plenum GM intake manifold with an Edelbrock Performer RPM Air Gap (PN 7562).
Exhaust: 2-inch headers, 3-inch Flowmaster dual exhaust with H-pipe and Flowmaster Super 40 mufflers.
Test 3 - After installing the 454 H.O./502 H.O. steel-roller camshaft (PN 24502611) with 211/230 degrees of duration at 0.050-inch lift, we generated an incredible 663 lb-ft of torque at 3,600 rpm. Sure, peak horsepower dropped, but all this torque could move a freight train. Maximum camshaft lift with the 1.7:1 rocker ratio is 0.510/0.540 and we ran 33 degrees total advance.
Exhaust: 2-inch headers, 3-inch Flowmaster dual exhaust with H-pipe and Flowmaster Super 40 mufflers.