Project 981 Cayman

Jon purchased a 981 Cayman as a fun weekend car that could see light track use. While the 2.7L 275HP Flat 6 made great sounds and carried plenty of punch to enjoy, Jon chose to take his Cayman to the next level with a 3.8L X51 Engine Swap. 

Let's take a closer look at how this modest car was transformed into the ultimate Porsche build.


At quick glance, one may think the Project 981 Cayman is a GT4. Few will know this car started as a base model Cayman. Jon always enjoyed the look of the 981 but loved the look of the GT4. So, he opted to swap the front bumper for the GT4 bumper. As part of this conversion, he also swapped all the ducting behind the bumper to maximize the OEM design, helping dissipate heat on the track.  

Around the back of the car, the Cayman features a TWL Carbon Fiber diffuser and duck tail spoiler. Jon wanted to keep the look simple and classic and took some inspiration by the 991 GT3 Touring to form the exterior modifications.


Suspension / Brakes / Wheels

The Project 981's main goal was to remain street compliant, however, Jon planned to take the Cayman to various HPDE and track events. 

For that reason, he went with the JRZ RS2 Touring coilover kit. This kit reuses the factory top mounts to remain a comfortable cruiser on the street but leverages 2-way adjustable dampers. The handmade coilovers from The Netherlands provide a wide-range of adjustment that shaves seconds off lap times at the track. 

With the additional 180+ HP, slowing the car is an important detail. Jon chose to swap for the 6-Piston 991 Carrera S front brake calipers. They are the PCCB option so are coated in yellow for a nice contrast. Out back are the calipers shared on the 718 and 996 Turbo. This set-up is a 100% bolt-on without any modification. Jon also upgraded to 2-Piece Giro Disc 350mm rotors both front and rear and finished things off with Goodridge Stainless Steel Brake Lines. 

Jon chose to have a custom set of BC Forged RZ05's finished in Matte Black for wheels. They are very strong, lightweight and provided a wider track allowing for more mechanical grip. 

Wheels: (F 19x9 ET50 - R 19x10 ET38)
Tires: (F 265/35/19 - R 285/35/19)


Engine / Transmission

Jon was able to source a 3.8L X51 engine pulled out of a wrecked 991.1 GTS. The X51 package that comes standard in the 991 GTS adds several key upgrades that increases horsepower from 400 to 430. The X51 package includes smooth ported heads, a new set of camshafts with higher lift and duration and also a unique intake manifold that features some Porsche wiz-bang variable resonance valves inside. 

The engine arrived with just 28K miles on it but with the motor out, we replaced all major wear items, seals/gaskets and spark plugs to refresh the engine. 

The base transmission was reused and maintains a shorter ratio gearbox compared to the GT4. Inside, Jon installed the BBI Sport Clutch Kit and Lightweight Flywheel. The transmission outputs to an OS Giken Limited Slip Differential (LSD) to properly put the power to the rear wheels. Connecting the bulked up transmission is a set of Numeric Racing Cables secured to the riffle action shifter. This ensures that every shift comes out precise and quick. With a quick heel-toe, the combination of the quicker revving engine and close shift pattern gives it an amazing feel. 

Also equipped behind the front bumper is an OEM Third Radiator kit. This helps provide maximum cooling for the car, especially handy for hot summer track days. 


Behind the engine sits a set of Soul Performance Competition headers connected to their Valved Cat-Back system. This combination keeps things relatively tame with the valves closed but a quick open of the valves, it transforms the car to a cup-car sound heading down the main straight at Sebring with the exhaust tone bouncing off the walls. 


Jon decided to keep things pretty basic inside the car. He's still waiting to install his SRP Racing Aluminum Pedals. The base Cayman came with heated & cooled base seats with a dual zone climate function. This was the extent of the option list, so for the meantime Jon is enjoying the versatility the seats provide. 

Attached on top of the Numeric Racing Shifter arm, lies a Raceseng Prolix weighted shift knob. This knob features machined engraving and finished in a wrinkle black textured finish for easy grip and control. The extra weight of the knob allows for easy transitions when rowing geats. 

What's next for Jon?

Jon is considering adding some aero bits to improve the performance on track with the Cayman. The car features plenty of power, plenty of stopping power and amazingly balanced handling. With the addition of making the car a bit slippier through the air, it should create something GT3 owners might get excited to see. The fine tuning on the car is still an ongoing project. Jon plans to finish dialing in the power and getting some dyno figures up shortly. He's shooting for over 400whp on a DynoJet dyno this coming spring. 

With the investment and set-up of the car, Jon plans to keep the Project 981 Cayman for quite a long time. The chassis has just 12K miles on it and the motor just over 1k miles and counting. It provides an amazing driving experience that can be comfortable and fashionable on the street but can also represent Porsche on the track. If the car does become a little more track oriented in the future, seats and a harness bar are on the top of the list. Jon also expects to be presenting a new Cayman build (987) that will feature even higher power output, stay tuned to Flat 6 Motorsports on social media to follow along for announcements on that. 

Taken by: Evan Trudeau