Porsche's flat-six engine was extensively reworked with four-bearing racing cams, high compression pistons and twin-spark cylinder heads with bigger valves. As a result, the power output increased from 210 hp in the 2.7 to 300 hp in the 2.8 RSR. To compensate for the extra power, larger 917-type brakes were fitted and the wheel arches were extended to make room for grippier nine-inch wheels at the front and 11-inch wheels at the back. While the 2.7 RS was already as light as a feather, the 2.8 RSR weighs just 1,851 pounds thanks to weight-saving measures such as Perspex glass, a lighter flywheel, and a smaller cooling fan.
This is even more impressive when you consider that Porsche had to strengthen the chassis to allow the car to cope with the demands of endurance racing.