GMS offers four stages of...
GMS offers four stages of ported heads. This engine features a set of Stage 3 Standard Race Port heads. They flow 209.5 cfm through the intake at 0.500-inch lift. Moving to the 0.600-inch and 0.700-inch-lift range, those flow numbers increase to 210.2 cfm and 211 cfm, respectively.
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.
On the exhaust side, the port...
On the exhaust side, the port flows 177.8 cfm at 0.500-inch lift. At 0.600, that number increases to 181 cfm, and finally 185 cfm at 0.700-inch 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.
In all, there are 24 valves...
In all, there are 24 valves in Ford's latest V-8 engine for the Mustang. That works out to three valves per cylinder.
Comp Cams was tapped for a...
Comp Cams was tapped for a set of sticks since two are required for the Three-Valve modular motors. We used PN 127600 camshafts.
The sprocket is bolted back...
The sprocket is bolted back on to the camshaft end.
Variable camshaft timing is...
Variable camshaft timing is a reality thanks to a system that involves engine oil moving in and out of the cam sprocket to adjust the timing-while the engine is moving. Oil fills the reservoir and physically moves the cam timing. It is controlled by a solenoid, which receives commands from the ECU.
A Comp Phaser Limiter is installed...
A Comp Phaser Limiter is installed in the cam sprocket to limit its movement. This piece doesn't lock out the variable cam timing, but it limits the range of motion. The limiters allow for larger camshafts without the fear of interference between the piston and the valves. If the cam timing is not limited or eliminated, interference can be problem. The limiter kit also allows for stronger valvesprings to be used, which under normal circumstances would snap the stock variable-cam-timing components.
A Turbonetics 76mm turbocharger...
A Turbonetics 76mm turbocharger features dual ball bearings for quick spooling. This turbo is capable of 800-plus rwhp with the 3-inch exhaust system.
The cam sprocket is bolted...
The cam sprocket is bolted back on using 85-lb-ft on the Snap-on torque wrench.
GMS includes high-flow catalytic...
GMS includes high-flow catalytic converters in its kit to keep the system emissions compliant.
A massive MAF sensor housing...
A massive MAF sensor housing is included in the kit to prevent any sort of restrictions. The sensor is of the blow-through kind.
Our test vehicle saw a maximum...
Our test vehicle saw a maximum of 13.25 psi due to it running on only 91-octane pump fuel. Despite the boost limit, the 297ci engine pounded out 585 rwhp and 634 rwtq! The air/fuel ratio ranged from 10.8 to 11.5, plenty safe for a turbocharged engine. Ray McClelland, formerly of Full Throttle Kustoms, is now the manager of engine development and tuning at GMS. He handled all of the tuning for this application.
Here is an S197 with a GMS...
Here is an S197 with a GMS turbo kit installed. It fits nice under the hood and offers plenty of punch.
The massive twin-core Spearco...
The massive twin-core Spearco intercooler is nestled under the bumper and receives plenty of fresh air.