The engine

This part of the story initially takes us back in time to the early days of racing with the 911.

The 916 Engine

The Porsche 916 engine is the most unknown, but also the most fascinating 6 cylinder race engine the Porsche engineers, namely Hans Mezger and his team mate Valentin Schaeffer, ever developed. The work on this engine started early 1967, when Ferdinand Pïech pushed the development of powerful engines for the Porsche race cars – driven by the slogan: “Win on Sunday – Sell on Monday”. The engineering team proposed a high rev, chain driven 4-camshaft concept on the basis of the 2.0-liter 911 engine. Such an engine could fit in 911 race and rally cars, and serve as a cost-efficient way to validate the concept for the required 8- and 12-cylinder race engines. The engine was assigned code “Typ 916”, and parts for about 10 to 20 engines were ordered. Probably only four or five of these engines were actually assembled in Porsche’s engine workshop, mainly used for dyno runs, but also fitted into a 910 car for actual track testing.

The first prototype of a 2,0 litre engine produced above 230 hp , close to the value the engineers had calculated.

However, during the first test runs, FIA changed the rules for “Sport Prototype” cars, and to quickly match the new specifications, the engineers proposed to modify the 916 engine by adding two cylinders and increase the displacement. The resulting 3.0-litre 8-cylinder race engines became famous in the 908 race cars, whilst the 916 concept of a chain-driven 4 cam engine was applied as well in the development of the 12-cylinder engines for the iconic 917 race cars.

As the race department was busy with these projects, no resources were available to further develop the 916 engines. The engines were thus handed over to the “Rally- and Kundensport” department, which was at that time also in charge of the 911R.

The 911R, with only 20 cars ever build, was meant to be an extremely light race car, thus the “normal” 911 was stripped of weight in every aspect possible, resulting in a final weight of just 820 kg.

The car was intended to carry a race prepped S engine of 210 hp, resulting in an impressive power to weight ratio of one to four. These few 911 R cars can truly be regarded as the ancestors of many more race cars to come on the basis of the 911.

The rally & “Kundensport” team installed and tested the 916 engines they had received from the race department in several of the R cars, and one can easily verify if a 916 engine was ever present in a given 911R, as the bigger chain-housing requires a triangular cut into the sheet metal next to the right engine mount.

With the additional power of the 916 four cam engine, a lightweight 911R must have been a truly unique experience, even more so when they experimented with bigger displacements such as 2,4 litres. These engines may have produced close to or even above 250 hp.

With just 20 R-cars build, and with the 916 engines required to compete in prototype class, opportunities were pretty rare to race the engine with a chance of success.

Thus, only few official missions are documented, such as a Solitude race and the 13th Tour de Corse in 1968, and an attempt in Targa Florio in 1969. Further the French driver Larousse may have entered with a 911 fitted with the 916 engine in the 1971 Lyon- Charnonnières rally.
Unfortunately, none of these events became a success, not because of the engine, but due to other failures such as broken differentials, oil leaks, fires and accidents.

Check futher information:
article in Porsche newsroom: R = Racing: The historical roots of the 911 R
thread at Early 911 S Registry: Four-Cam 911R’s

With some further fine tuning this engine would certainly have added another 10 to 20 hp, but in the end the 916 engines turned out to be too costly for production cars, and the 911R was discontinued due to concerns of the sales department. Most 911R cars were sold to private racers and business partners, and the 916 engines and parts went on sale as well – a usual practice at Porsche that time.

The KMW team from Rosenheim snapped some up, and the 916 engines were subsequently fitted into race cars such as the KMW SP 20 monocoque and in hill-climb cars, and raced over the following seasons, however the full potential of this incredible 6-cylinder engine was never fully exploited.

THE 916 RELOAD

Fast forward to 2015, when several Porsche race veterans came together and exchanged memories. Around that time, the new 911R was on the horizon, so naturally, the topic of the unfinished development of the 4-cam engine for the 911 came up over a beer or two, cumulating in a somewhat stealth plan to recreate the engine. In best Porsche practice, learnings and improvements from the 908 and 917 engine developments were supposed to be implemented in the recreation, and a 2,5-liter layout was agreed as starting point.

Luckily, the Porsche veterans had retained a lot of drawings, plans and notes in their archives, and a number of original parts for the 916 engines could be surfaced through their networks, whilst some available parts of the 908 and 917 engines could be used or modified as well.

With outstanding craftmanship, ingenuity and persistence a boutique engineering workshop in southern Germany close to Stuttgart, planned for a small run of these engines, and a first prototype (#916-P1) was completed about two years later.

When tested on the dyno and on the road, just minor adjustments and modifications were required for the next few engines to be assembled.

Subsequently the engine was on display at the Straehle Porsche Swap in Fellbach in 2019,  and at Rennsport Reunion in the US the same year.  

As per below dyno sheet, engine #916-P5 produces 263 hp@8000 rpm,
with a redline of 9000 rpm.

As a gift to the cars 52nd birthday in 2020 that engine was fitted into the slate grey 911 SWB (VIN # 11 93 51 3).
As it is a race engine it will be primarily enjoyed and driven on race courses and track days across Germany, and will occasionally also be on display at Porsche events.

Now live begins at 4000 rpm for # 11 93 51 3
May the 4-cam force be with you !

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please direct suggestions – criticism – comments to hallo@911rr.de