Forged Diamond pistons feature...
Forged Diamond pistons feature a dished design that helps maintain a supercharger-friendly 9:1 compression ratio.
Firm Foundation
The basics of the engine combination include the iron LSX block with 4.125-inch bores, a forged crankshaft delivering a 4.000-inch stroke, and forged rods and pistons. The short-block assembly is similar to that used in GM's LS7 engine, but with forged Oliver rods and Diamond pistons, which stand up better to the heat and pressure generated by a supercharger. (The LS7 uses cast pistons and featherweight titanium rods.) The pistons feature a dished design in order to permit the lower compression ratio (9:1) needed for a supercharged setup running pump gas.
The heads are prototype LSX aluminum parts obtained through Thomson's secret pipeline to GMPP. These feature the same design as the LS7 heads but with additional, cast-in mounting holes to allow the use of extra head bolts (six versus the production-style four). The heads offer a tremendous flow rate of approximately 380 cfm on the intake side.
Feeding the big heads is the aforementioned 2.3L blower, which features Eaton's new four-lobe rotor design to broaden its effective range. An LS7 90mm electronically controlled throttle body was adapted to the blower's inlet, and an air-to-water intercooler was installed to enhance performance and durability. Harrop Engineering supplied all of the necessary pulleys and drivebelts for the supercharger, but the eight-rib pulleys necessitated a custom crankshaft balancer with an extra rib cut into it.
The engine uses a stock LS7 camshaft, which delivers 0.591 inch lift (intake and exhaust) and 230/231 degrees of duration; again, it's one of the many off-the-shelf parts used in the combo. Aside from a set of custom, long-tube headers fabbed in Thomson's shop, the rest of the assembly is composed of pretty straightforward stuff. Engine operation is overseen by a new GMPP controller that's based on the production-style E67 brain.
Additional details of the engine combination include:
* 62-lb/hr ACCEL fuel injectors
* LS7 ignition-coil packs
* LS7 dry-sump oiling system with two-stage internal oil pump
* LS7 oil pan
* Custom headers with 2-inch primaries and 3-inch collectors
 A stock LS7 cam delivers 0.591...  A stock LS7 cam delivers 0.591 inch lift (intake and exhaust) and 230/231 degrees of duration. Its high-rpm performance was deemed a good match for the heavily boosted engine. |  The heads are something special....  The heads are something special. They're prototype versions of GMPP's LSX heads, which are based on the LS7 units but feature two additional head-bolt provisions. The additional bolt holes permit more-secure sealing of the head, which is particularly important in supercharged or nitrous setups. |  The LS7-style intake ports...  The LS7-style intake ports are huge, straight pathways to the combustion chambers. They're capable of flowing about 380 cfm on the intake side. |
 Neither small nor huge, the...  Neither small nor huge, the LS7-style combustion chambers of the LSX heads come stock with 70cc volume. The valves to be inserted here are huge 2.165/1.600-inch components held at a 12-degree angle. |  A standard LS7 valvetrain...  A standard LS7 valvetrain is used, including the pushrods, springs, and offset (intake-side) rocker arms. |  Ignition chores are handled...  Ignition chores are handled by a stock LS7 ignition system, which uses individual coils for each cylinder. |