Swindon Powertrain has sold more than 100 units of its M64 cylinder head kit, a 24-valve upgrade designed to increase performance and rev capability in 964- and 993-generation Porsche 911 engines.
Launched at the end of 2023, the retrofit kit replaces the original two-valve-per-cylinder layout of the M64 air-cooled flat-six with a four-valve architecture, improving airflow and combustion efficiency. The upgrade enables engines to rev up to 12,000rpm and also increases power and torque, with a weight reduction of 3.5kg compared with the standard configuration.
The cylinder heads are cast in the UK using aerospace-grade A356 aluminum CNC-machined in-house at Swindon Powertrain’s Wiltshire facility in the UK. Kits have been supplied to engine builders and specialists globally, including in Europe, the USA, Japan and Australia, for road and track applications.
“Relying on low-flow, two-valve-per-cylinder architectures, the M64 air-cooled engines typically have restricted air flow into the combustion chamber, while the need for heavier springs stresses the rockers and limits RPM,” explained Sylvain Rubio, technical director at Swindon Powertrain. “Our M64 cylinder head kit is helping deliver more power and performance to a new generation of upgraded Porsche 964 and 993 models, benefitting from the latest materials and the finest of CNC machining tolerances.”
The 24-valve design increases peak airflow by around 40% compared with the standard 993 configuration. The kit includes titanium inlet and exhaust valves, along with associated valvetrain components such as springs, caps, collets, shims, finger followers and shafts, as well as camshafts, cam covers and timing drive input.
Among adopters is UK-based Thornley Kelham, which is using the cylinder heads in its limited-edition European RS model. The program will produce 15 vehicles, with customers offered either a 3.6-liter engine delivering more than 380bhp and 290 lb-ft of torque with a 10,000rpm limit, or a 4.0-liter unit producing over 425bhp and 325 lb-ft with a 9,000rpm limit.
“We’re proud to be helping so many engine builders and 911 enthusiasts around the world unlock substantial extra power and torque to create truly standout builds with this high-revving upgrade,” added Raphaël Caillé, managing director at Swindon Powertrain. “Pushing the boundaries of engineering – often beyond what seems conceivable – is a challenge we thrive on. We’re never content to stand still.”
The company is developing other high-performance concepts, including a flat-eight engine. In late 2025, Runge Cars confirmed that it is working with Swindon Powertrain on a 5.3-liter, 32-valve, air-cooled unit.
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