PopJohn offered a brand-new original cylinder case for the buildup, so the bore remained at 4.00 inches. The block was decked and honed with torque plates, and the rotating assembly was balanced and blueprinted. In keeping with the purity of the project, the motor uses stock GM forgings (pistons are 11.0:1) that were part of the original, including the fabled "pink" connecting rods and a GM solid lifter stick (0.484/0.484 inch lift, 317/346 degrees duration at 0.050 inch). A Cloyes True Roller timing gear cinches it to the steel crankshaft.
The oiling system is wholly GM. In the matter of breathing, the refurbished double-hump cylinder heads host a three-angle valve job, stock valves and springs, and Comp Cams 1.5:1 Pro Magnum rockers and hardened pushrods.
The original dual-plane manifold is topped with a Speed Demon 750-cfm double-pumper carburetor (converted to mechanical secondaries) sucking through K&N filtration. An MSD 6A box and Pro Billet distributor, coil, and wires make a very capable ignition system, and timing is set at 14 degrees at idle. Hooker Super Comp headers maintain 151/48-inch primary pipes. Further, the cylinder block was peppered with ARP fasteners. The original solid lifter LT1 produced 360 hp, but power figures for this updated version are not available at this writing.
The original M21 manual got complete rehab and takes torque from a Centerforce Dual Friction clutch assembly and passes it to the stock rebuilt driveshaft. The terminus is the original ZQ9 12-bolt fitted with a Posi-traction differential and 3.73:1 gears.