Filling the eight holes are Manley Platinum Series forged pistons-built to GMS specs, including coated skirts. The pistons are connected to Manley forged-steel connecting rods. The army of eight slugs and rods are connected to a 3.750-inch-stroke, forged-steel crankshaft. Together the bore and stroke sizes combine for an LS-slaying 297 ci. The company also offers a larger bore size of 3.572, to bring total cubes to 302.
The short-block is complemented with a top-end that consists of GMS Three-Valve heads, which are OEM pieces that have been run through the CNC machine. The heads also feature larger valves than stock.
GMS offers four stages of heads that begin with flowing 178.5 cfm on the intake and 136.2 cfm through the exhaust ports (at 0.500-inch lift) to a race-ported set that flows 227.3 cfm on the intake and 196.4 for the exhaust, at 0.500-inch lift. The Stage 4 race numbers increase to 251.6 cfm (intake) and 207 cfm (exhaust) at a racy 0.700-inch lift. In comparison, the stock ports and valve configuration flow 170.2 cfm through the intake ports and 129.5 cfm on the exhaust side, at 0.500-inch cam lift.
The Three-Valve engine features overhead camshafts, and while the stock sticks work well in most turbo applications, GMS felt this particular engine could make more power with an aftermarket pair. The team turned to Comp Cams and its SPR line of cams. Since the Three-Valve engines feature variable valve timing, Comp offers its more aggressive cams with a Cam Phaser Limiter kit. This limiter prevents too much movement of the cam timing, allowing for larger-than-normal camshafts. We used PN 127600 camshafts, which offer an aggressive idle and help the engine scream to 7,000 rpm. These sticks measure 0.547 on the intake and 0.560 for the exhaust lift. Duration at 0.050-inch is 237/244 degrees.
The stock intake manifold is utilized, but the boost first passes through a GMS twin-bore (62mm each) throttle body. The turbo system is, of course, the single Three-Valve setup from GMS. It boasts a Turbonetics 76mm dual ball-bearing turbocharger and twin-core intercooler. The turbo system is capable of 800 rwhp in its 3-inch exhaust configuration.