Rock West GTS

904 left sideThe early Sixties were a truly remarkable time for road-course racing. After Carroll Shelby transformed his 289 Cobra from a street fighter into a track champion, Corvette chief engineer Zora Arkus-Duntov counter-punched with the Grand Sport version of the Sting Ray. And yet another world-class race car entered the fray: the Porsche 904.

Debuting in late ’63 for the upcoming season as a successor to the 718, it raced in both ’64 and ’65. Even though it didn’t gain quite the notoriety and longevity of either the Cobra or Grand Sport, it was a force to be reckoned with, doing far more with less, and winning on a number of race tracks in the FIA-GT class.

Instead of a big V-8, the 904 initially ran an overachieving, four-cam flat four producing a then-remarkable 196 horses. Thus equipped, a 904 won overall at the Targa Florio and went on to demonstrate remarkable durability throughout its racing career, almost always finishing, if not taking First place. Later models were fitted with a 911’s flat six, and a few factory race cars even had a flat eight.  

904 right frontA street-legal version became available as well in order to comply with FIA requirements. Orders far exceeded the minimum required by homologation rules, as the car’s lithe shape and mid-mounted, hemi-style engine were compelling attributes. Approximately 120 total units were built encompassing all engine variants.

Like the Cobra of the same era, the 904 had a ladder-style frame, but stiffened by bonding with a fiberglass body (a first for Porsche). Since outside contractors produced the bodies, laid up with chopped fiberglass, their panel thickness was inconsistent, and the weight of the cars varied. Race-prepped models fitted with a four-cam tipped the scales at only 1443 pounds, optimizing the power/weight ratio and delivering a 0-60mph time of less than six seconds. The aerodynamic shape, considerably sleeker than the Cobra or the Stingray, allowed for a top speed of 160 mph.

Another innovation in the design was the coil-spring suspension with unequal A-arms up front, replacing the traditional trailing arm setup and swing-axle rear.

Today, Rock West Racing carries this spirit of engineering innovation forward with its RW GTS. The body is still made of fiberglass, but with a much more precise lamination process and modern materials for additional reinforcement and stiffness. (Carbon fiber panels are being considered as a future option.) The shape of the RW GTS was meticulously reproduced after careful examination and measurements of two original 904s to ensure extreme accuracy. (The rear wheel wells in particular keep the authentic form and line, unlike some replicas that have widened fenders.)

As with the original car, the body is bonded to the chassis for extra rigidity, but Rock West Racing’s frame is stronger, based on Porsche’s later-model 906 and 910 designs, and can be more efficiently manufactured as well. The frame members consist of 1.5-inch chrome moly tubing with a .090” wall thickness, further reinforced with a roll bar tube wall specified at .125”.

The suspension on the RW GTS has been modernized as well. At the front are custom-fabricated, unequal-length A-arms made of chrome moly tubing, and fitted with Porsche 944 hubs and disc brakes (Wilwood brakes are optional), and steered by either a 911 or a 944 rack-and-pinion unit.

At the rear are upper A-arms and lower H-arms, fitted with micro-stub axles (half shafts). Fox shocks and Eibach springs are mounted at all four corners (Bilstein shock mounting provisions are in the works as an option).

Two different body models are available, one matching the four cylinder cars with small side vents and a rear deck grill spanning between the roof buttresses and the other body matching the later 904/6 cars with large side vents (“elephant ears”) and the rear deck grill blocked off.

Typical current drive train is the 911 six-cylinder engine mated to a 901 gearbox (as used in the Porsche 914).  If a client happens to have a 4 cylinder 4-cam engine for their car, chassis mounting provisions can be accommodated.  No matter which body style is chosen, the RW GTS is suitable for street duty, and even higher performance cars are available on a special-order basis.

IMG_5678Due to the sophisticated chassis design and extra mold work involved in constructing a coupe, along with the rarity of this reproduction that requires a number of custom components, the RW GTS commands a premium price.

The Builder Package ($47K) comes with the body fitted to the chassis and all doors, hood and the rear body section mounted, hinged and latched. The kit also includes many of the unique components that are no longer available, nor easily sourced or fabricated, such as the windshield, headlight covers, fuel tank, and oil reservoir. Completing the car’s assembly from the kit requires installing the drivetrain, electrics, windshield, wheels, tires, paint and cockpit upholstery.

A Roller ($78K) is essentially complete, except for the addition of customer-supplied drivetrain. Sliding windows are standard items on all models, and the fuel-filler cap can be either side-mounted or center-mounted, depending on customer preference.

As with the original 904, the RW GTS is essentially a race car for the street. It can be piloted smoothly down a boulevard, and then tear up the track at a moment’s notice. Its true to form appearance is as original as possible yet significantly improving on the design with modern engineering; thus the RW GTS allows drivers to relive that classic era of road-course racing in a contemporary design.