With few entrants ready, willing and or able to compete in the 3 litre / 183 cui prototype sports car class in April 1968 the governing CSI reduced the production numbers mandated to compete in the 5 litre / 302 cui sport category from 50 to 25.

With this change in regulations Porsche saw an opportunity to build a 917 Coupé powered by a Type 912 12 cylinder motor that would give it a shot at winning the 1970 Le Mans 24 Hour race.

An unforeseen benefit of the Porsche 917 Le Mans programme arose when Porsche decided to have a crack at the North American Can Am series for unlimited sports cars in mid 1969.

For it’s first attempt at the Can Am series Porsche built two 917 PA spiders one of which would enter the fray midway through the 1969 Can Am series driven by Jo Siffert.

Today’s featured car chassis #917-027 was the first of the two chassis and it was retained at the Porsche factory for development purposes.

It soon became apparent that the 917 PA was too heavy and not developing enough horsepower to compete with the dominant McLaren’s driven by Peter Revson and Denny Hulme so Porsche looked at two ways of getting more horsepower from the type 912 flat 12 motor they had developed originally to tackle Le Mans.

One was to turbocharge the existing engine and the other was to add 2 additional cylinders to either end of the 912 flat twelve whose cam shafts were centrally driven.

After testing the 840hp 6.700 litre / 408.9 cui sixteen cylinder car Mark Donohue described it as a monster which in turbocharged form might have produced 2000hp.

However the engineers at Weissach came to the conclusion that the 1000hp and more available from the turbocharged 12 cylinder motor would be more than sufficient to do the job, and so it proved.

George Follmer captured the 1972 Can Am title driving Roger Penske’s L&M Porsche 917/10 after Penske’s No 1 driver Mark Donohue was injured and had to miss 5 rounds of the nine race series.

Mark Donohue followed that up in 1973 by capturing the title in Roger Penske’s Sunoco Porsche 917/30.

Thanks for joining me on this “Sechzehnzylinder Monster” edition of “Gettin’ a li’l psycho on tyres” I hope you will join me again for Ferrari Friday tomorrow. Don’t forget to come back now !