The crew at GMG took on the challenge of shoehorning the new engine into the older project. Custom engine and tranny mounts were fabricated so the taller intake plenum would fit inside the Boxster's cramped engine bay. Once inside, a solution for the variable valve timing had to be found. GMG used the heads from an early 3.4-liter 996 that utilized the same single-cam system, but the ports were revised to handle the added airflow. The cams were re-profiled to match that of the X51 to ensure the same performance. The new wiring harness and DME were also sourced from a 3.4-liter 996. This allowed the use of a mechanical throttle body, which simplified things greatly. A new cold-air intake system was custom fabricated and the fueling system came from the X51.
GMG decided a Cayman S exhaust would be the best option for fit and emissions. The factory catalysts are retained, keeping things simple and legal. A sport exhaust is always an option when looking to save some weight and add power.
Electronic tuning was left to GIAC. While this swap is a little out of the ordinary, it isn't that much of a stretch for the company. A custom lightweight flywheel and Sachs racing clutch were installed to handle the extra torque. There's a certain amount of doubt right now as to how long the factory transmission will hold together with the newfound power. No doubt it'll be the next mod on the list. It's still unclear whether a full performance rebuild and reinforcement will be a better route than a complete swap.
With the install complete, GMG corner-balanced the car to compensate for the new engine weight. Right now, the car idles just like factory and pulls off the line with no effort at all. The clutch is surprisingly easy to manipulate and no ill effects have been found concerning the lightweight flywheel.
This may seem like a ridiculous way to go instead of just buying a newer, faster car to begin with. If you're lucky, you can find a Boxster with a blown engine for less than 10 grand. The engine itself will be about another 10, so without labor you're still around $20,000. It gets even more expensive when thinking about the brakes, suspension, aerodynamics and so on. However, if you have a Boxster that's already modded, then the engine swap may make sense. And surprisingly, swaps like this seem to be catching on, using everything from late-model Boxster S motors to GT3 powerplants swapped into older cars.
Our editor swears the Bidrawnxster is finished. I'll believe it when I see him drive it to work. Especially when I see a tell-tale trail of transmission parts in a month or so.