Porsche claims that the new 911 S/T is the most exciting 911 road car yet, but certain specialist manufacturers might have something to say about that. The appetite for 911-based restomods from the likes of Singer and Theon Design shows no signs of slowing, and in the wake of this trend, Swindon Powertrain has devised an engine upgrade kit to take air-cooled 911s to the next level. 

The British engineering firm's new retro-fit cylinder head, compatible with 964 and 993 models, unlocks the ability to rev to 12,000rpm thanks to completely redesigned valvetrain components and airflow geometry. Provided the rest of the motor is built to take advantage of these parameters, the kit opens the door to what could be the ultimate air cooled 911 engine. 

Porsche designed 964 and 993 engines with two valves per cylinder, but Swindon Powertrain’s solution uses four valves per cylinder. Each valve is smaller than before and formed from titanium, which allows the engine to spin up to higher revs without putting undue stress on the rockers. 

Aside from the headline rpm figure, the kit also provides significantly better air flow into and out of the cylinders by doubling the number of valves (Swindon Powertrain has measured improvements of 40 and 60 per cent on the inlet and exhaust flow respectively). Cast from aerospace-grade aluminium, the cylinder head kit also saves 3.5kg compared to the standard setup.

All the major components required to fit the new cylinder heads are included, such as valve springs, caps, shims, finger followers and cam shafts, topped off by a new set of cam covers. Swindon Powertrain can also supply custom pistons to utilise the full potential of the new heads, along with inlet porting and unique cam profiles tailored to the engine’s specs and intended use. Costing £29,950 plus VAT, Swindon Powertrain offers a one-year warranty with each cylinder head upgrade kit.

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