Swindon Powertrain has reached 100 sales of its M64 Cylinder Head Kit, a 24-valve conversion for Porsche 964 and 993-generation 911 engines that pushes a classic air-cooled flat-six architecture into a far more aggressive performance range.
Launched in late 2023, the kit replaces the original two-valve-per-cylinder arrangement with a four-valve layout designed to improve breathing efficiency, raise power and torque potential, and support much higher engine speeds. Swindon says the package is 3.5kg lighter than standard and can support valvetrain speeds up to 12,000rpm, while peak flow is said to increase by 40% versus a standard 993 configuration.
The engineering is as important as the headline number. The cylinder heads are cast in the UK from aerospace-grade A356 aluminium and CNC-machined in-house in Wiltshire before assembly into a broader package that includes titanium inlet and exhaust valves, springs, caps, collets, shims, finger followers, shafts, camshafts, cam covers, and timing-drive input. In effect, it is less a bolt-on tuning part than a reworked top end aimed at specialist builders who want modern breathing and valvetrain capability without abandoning the M64 platform entirely.
Swindon says the kits have already been shipped to engine builders across Europe, the US, Japan, and Australia. Among the named adopters is Thornley Kelham, which selected the heads for its limited-run Porsche 911 European RS programme, offering 3.6-litre and 4.0-litre 24-valve specifications with outputs stretching beyond 380bhp and 425bhp respectively.
Sylvain Rubio, technical director at Swindon Powertrain, said the original two-valve architecture limits airflow and raises valvetrain stress at higher engine speeds, while managing director Raphaël Caillé said further high-performance developments are on the way. One of those is already in motion: the company has also been working on a flat-eight air-cooled engine programme with Runge Sportscars. The 100-unit milestone therefore says something broader about Swindon’s position in the market. There is now enough demand in the premium restomod and race-engine space to support serious low-volume manufacturing, not just one-off engineering indulgence.
