Michael Galimi
October 1, 2009
Photos By: Courtesy Of Granatelli Motor Sports
Here is a view of the side bolt for the main cap.

"For comparison sake, a '93 Cobra is rated at 230 hp from the factory. It makes 370 hp at 10 psi of boost. A '96 Two-Valve GT engine is rated at 215 hp from Ford. Adding the same 10 psi of boost brings output to 378 hp. The number seems insignificant, but consider that number is an increase across the board. If you started out with a good performance motor that made 300 hp in naturally aspirated trim, then added a blower (regardless of type-Roots, twin-screw, or centrifugal), the difference between the conventional pushrod and OHV motor would be 24 hp more.

Another nice feature of the Three-Valve blocks are the knock-sensor bosses in the upper valley of the block.

"At the dragstrip, where 15-20 psi of boost is common, the numbers get more lopsided. A pushrod engine with 300 hp at 15 psi would make 591 hp and a mod motor would produce 615 hp. These numbers are based on an SAE standard, but when factoring in various camshaft profiles, the percentages can become even greater in favor of the mod motor."

The GMS crate engine boasts features that lend themselves nicely to big horsepower. GMS can tailor the engines to fit your requirements, but the one we covered is designed for a boosted application.

The team started with a stock aluminum Three-Valve block. Despite their aluminum nature, these blocks are extremely durable and up to the task of handling well-over 800 rwhp. GMS had the bore cleaned up and the final measurement is 3.552 inches.

Manley Platinum Series pistons are used for this application. The dish provides a 9:1 compression ratio, perfect for boosted applications. Some folks prefer to build lower compression ratios into the engine, but as long as the turbo isn't pumping out severe boost levels, a 9:1 compression ratio will work just fine. Stock Three-Valve engines in the Mustang GT features 10.1:1 compression.

In this application, the GMS test vehicle produced an impressive 585 rwhp on the in-house Mustang Dyno. Producing that amount of horsepower requires extra fuel, so GMS added the typical monster-sized fuel injectors (72-lb/hr), as well as larger GMS fuel rails and a custom fuel system designed by GMS.

The fuel system utilizes a bladder tank mounted under the hood. It keeps the returnless setup and stock tank, but the bladder acts as a separate return-style system. It is a trick setup that Granatelli brought over from his LS-engine based projects. Naturally, the ignition system is enhanced with GMS Pro Series X coil packs.

This engine ultimately found its way under the hood of an S197 Mustang belonging to Troy Coughlin of Jeg's Mail Order. It is an '07 Saleen Mustang that has received the complete GMS makeover with a full 1g-capable suspension system and the turbocharged stroker engine shown on these pages. These days, you just can't beat boost on top of a modular motor and companies like GMS make it easy.