The Swindon M64 Cylinder Head Kit is proving there’s serious appetite for high-revving air-cooled Porsche builds.
Less than two years after launch, 100 units have already been sold worldwide.
Introduced in late 2023, the upgrade is designed specifically for Porsche 964 and 993 models, transforming the character of the classic flat-six.
At its core is a newly engineered aluminium cylinder head with four titanium valves per cylinder, replacing the original two-valve setup.
The result is improved airflow, reduced internal mass and a significant uplift in both power and torque.
More striking, however, is its ability to safely push engine speeds to a claimed 12,000rpm—territory usually reserved for modern motorsport-derived engines rather than air-cooled classics.
Despite costing over £30,000 before taxes, demand has been immediate and global.
Around 15 kits have been installed in Thornley Kelham’s European RS builds, where they’re paired with either a 3.6-litre engine capable of revving to 10,000rpm or a larger 4.0-litre unit reaching 9,000rpm.
The remaining kits have been supplied to specialist engine builders across Europe, as well as in the United States, Japan and Australia, supporting a mix of road and track-focused 911 projects.
It’s a clear signal that the restomod and performance Porsche scene continues to evolve rather than plateau.
Swindon Powertrain’s managing director Raphaël Caillé points to the growing demand for more extreme, individual builds—cars that blend analogue character with cutting-edge engineering.
The appeal isn’t just about performance figures, but the experience: an air-cooled flat-six delivering a race-like intensity at five-figure revs.
Development isn’t slowing either. Swindon has already confirmed further high-performance projects are underway, including a 5.3-litre flat-eight engine for US-based Runge Cars.
Known for its hand-built, vintage-inspired machines, Runge’s collaboration hints at even more ambitious engineering to come.
For now, the Cylinder Head Kit remains available for those willing to invest in something truly distinctive.
And with triple-digit sales already achieved, the idea of a 12,000rpm air-cooled 911 is no longer a niche fantasy—it’s a growing reality.
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