- 608
- Italy
This 3.4 conversion is the popular extrapolation of the proven Ruf SCR conversion, first seen in 1978, which used 98mm barrels and pistons on the 3.0 litre Carrera and 911SC motors, to achieve 3.2 litres.
On the SPS car, those same pistons are married to the Carrera 3.2 crankshaft deliver 3.4 litres, with the blueprinted and balanced crankshaft joined to the new pistons with titanium connecting rods.
The lower reciprocating masses help the engine spin easily to its 8,000rpm cut-out, just above the point where it makes a healthy 340hp. The gas-flowed cylinder heads were modified for twin-plugs, while the ignition spark is looked after by a 964 Carrera distributor.
Substituting the K-Jetronic or Motronic single throttle body plenum style injection for a single choke per cylinder system, either carburettors or fuel injection, delivers a huge improvement in power, torque, throttle response and soundtrack.”
On this motor, Ruf uses a single throttle per cylinder set-up controlled by the Bosch Motronic 1.2 race system as fitted to the Porsche 962LM sports prototype racecars.
Those familiar with the technical specs of the famous Ruf Yellow Bird will recall that Ruf pioneered the use of this DME system on a road legal car. “This is exactly the same system we used on the Yellow Bird, sans the turbo boost control element,” said Alois Ruf.
Transferring the power and torque to the rear wheels is the job of a six-speed Getrag G50 gearbox. Ruf had to modify the rear torsion bar axle tube to take this gearbox, which does not normally fit pre-1987 911s.
The extra heft of the G50 gearbox takes the kerb weight of this car 20kg over the magic 1,000kg figure. While an original 308hp 2.8 RSR tips the scales at just over 900kg, it also has significantly less power and torque than this 3.4. But don’t forget that the raison d’etre of this car is to invoke the look and feel of the original while providing a higher standard of usability, comfort and reliability for regular use today.
I drove an original 2.8 RSR many years ago when no one but aficionados were interested in them and their values were still sane. It was a totally different feeling from the 2.7 RS. With 100hp more, and the hair trigger delivery of the slide throttle single choke per cylinder mechanical injection, it felt like a rapier compared to a broadsword.
With so much more power and even less weight to carry, the 2.8 RSR hurled you down the road where the 2.7 RS merely gathered speed rapidly. It felt sharper, more alive and very, very addictive.
Thanks to its lightweight internals, the balanced 3.4 litre motor revs freely and rapidly with an incisive throttle response that feels somewhere between the two original factory cars.
It is not as lively as the 2.8, which is essentially a race motor, and of course it has to pull an extra 120kg, but it still has a level of zing, for want of a better word, missing from modern engines with their single throttle body, plenum-based induction systems.
Its torque however, is greater than the RSRs, and the six-speed Ruf version of the Getrag G50 box makes full use of that twist even when you don’t use the generous 8,000rpm power band.
The G50’s action has a very different feel to the earlier 915 gearbox. It is more precise, more rifle-bolt like, and anyone who has driven 911s with both gearboxes will tell you which is which in an instant, even blindfolded.
It is only the wish for six forward ratios that makes the G50 necessary though, as I and many other 911 fans agree that the feel of a properly rebuilt 915 ‘box better suits the character of these older cars. As for torque handling capacity, installing steel synchros for the first two gears usually does the trick.
Despite the wide wheels and fat Yokohama AVS tyres, steering effort is still relatively low. Ruf’s expertly set up geometry ensures the absence of front axle histrionics on the local roads, which are consumed very rapidly indeed in the noble cause of having fun.
While the 3.4 RSR looks pucker from the outside, a glance into its cabin instantly gives the game away, but not in the way it does with many backdated invocations.
Here, the dashboard top roll is authentic 1973 911 with no later big air vents, and the deep bucket sports seats are period too. But the steering wheel rim is thicker than the original thanks to extra padding, and the Ruf instruments are late ‘80s style.
The rev counter is recalibrated so that the 8,000rpm redline is at 12 ‘o clock, the speedo reads out to 300km/h, and on the extreme right a bespoke combined Volt and Amp gauge replaces the clock.
The metal panel below the dashboard contains controls like the rotary knobs for the brake bias and the choke along with warning lights for oil temperature and a competition style master ignition cut-out. All the script is in German, like on the boost control knob on the floor of the Yellow Bird. This adds to the authentic classic Ruf feel.
The long, angled gear lever from a post 1987 Carrera 3.2 is another giveaway, as is the Ruf alloy pedal set. The car has a Ruf integrated roll cage, although the race style crossbars behind the seats and Schroth four point harnesses make a clear statement that this is a car born to be used on track.
I am not fully sure about the year
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