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Porsche Cayman GT4 Upgraded With GT3 RS Flat-Six Engine

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Track-focused Cayman now comes with almost 500 horsepower.

For the past several months, we've seen countless spy shots of the rumored Porsche 718 GT4 testing. Unlike the original GT4, which was powered by a 3.8-liter flat-six from a 911 Carrera S, this new car is expected to use a detuned 4.0-liter flat-six from the current GT3 that produces 500 horsepower.

If you just can't wait for Porsche to reveal the new 718 GT4, a tuner called DeMan Motorsports has you covered with a flat-six engine upgrade.

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Instead of going down the easy route by adding a turbo or supercharger, DeMan has bored out the 3.8-liter flat-six to 4.25-liters. DeMan previously offered a 4.0-liter upgrade but says this new 4.25-liter job is even more focused on delivering peak power.

The stock engine delivers 385 hp, though Deman says its new upgrade will produce 488 hp and 360 lb-ft of torque at the wheels. Factoring in a 15% drivetrain loss, this monster now produces 561 hp and 414 lb-ft at the crank - an increase of 176 hp and 105 lb-ft of torque over stock. This 4.25-liter GT4 is even more powerful than the current 911 GT3 RS.

DeMan has even posted a dyno video showing the car hitting its increased 8,000 rpm redline. According to Road & Track, optional titanium internals can further increase the redline to an eye-watering 8,500 rpm. So what's the cost for this incredible upgrade? $28,500, plus the cost of a Cobb access port.

DeMan says most of the customers interested in this sort of power increase have already performed other upgrades to their car, allowing the base price to remain fairly reasonable. Even when Porsche does reveal the 718 GT4, we know it won't be as impressive as this.