17 Jul 2017

Porsche 356 4-cam engine rebuild

A rare 2-litre Porsche 4-cam engine arrives at the Tuthill workshops for rebuild

We’ve just brought this 1962 Porsche 4-cam engine out of storage and into our engine shop to start the process of restoring and rebuilding it. It’s a complicated piece of engineering, which we are converting from a Type 587/1 Carrera GS to a 587/2 904 GT engine, using many factory parts and also some parts made back in the day by an F1 engine builder. The flat four will be an exciting rebuild to factory spec and we look forward to trying it on the road.

Also known as ‘Fuhrmann’ engines, the 4-cam engines were developed in the mid-1950s by Dr. Ernst Fuhrmann, who would go on to become MD of Porsche AG from 1972 – 1980. Fuhrmann was a genius in valve trains – his doctorate from Vienna University was granted following a study of valve trains in high speed internal combustion engines – and the four-cam engine utilised every ounce of his intelligence.

Fuhrmann’s groudbreaking Type 547 engine was a flat-four boxer engine, with two overhead camshafts per cylinder bank, all driven by bevel gears. The four camshafts contribute to prodigious power per litre for the period. Small wonder these race engines, first developed for the 550 Spyder, would go on to be used in 356 Carrera, 718 RSK, RS 60/61, and 904 GTS models.

For all of their power and technical fascinations, the 4-cam engines had many downsides. Not only were they tremendously complicated, they were also comparatively fragile. Few engineers fully understood these engines, with their flywheel camshafts and myriad bevel gear drives.

“These first 4-cam engines took a skilled man 120 hours to assemble and the timing alone could take eight hours – sometimes fifteen – if tolerances weren’t just right,” Fuhrmann is quoted as saying.  It is also said that two 917 engines could be assembled in the same time that it took to build one 4-cam Carrera engine, so it’s easy to see why many owners simply swapped them for larger 356 engines when they began to play up.

Many of these complicated engines were left abandoned in workshops all over the world when they began to cause trouble, and that is exactly how we acquired our 4-cam engine two decades ago. It is one of two 4-cam engines in our inventory so there are at least two rebuilds ahead! Keep following for more installments as the restoration progresses.