In 1974, Mercedes-Benz launched the W116 450SEL 6.9 – the world’s fastest-ever four-door production car.
Rated at 286bhp, it was the ultimate autobahn cruiser with a rated top speed of 140mph (Motor magazine verified this to be correct in-period) and it remained the world’s fastest four-door until the W126 560SEL of 1987, which was rated at 300bhp.
At 6834cc, to this day it ranks as Mercedes-Benz’s largest displacement post-war engine, and the largest displacement V8 ever produced in Europe since the 1930s – period.
The shock and awe that only a 6.9 can provoke is the tale of lore and legend, right down to the factory-specified tyres: Michelin XWX, as shared with the Ferrari Daytona – at £321 a corner. That’s £1,605 for a set of five.
And before you even draw breath on the rubber connecting the car to the road, there’s the dry sump engine: £25,000 for a full overhaul, plus the four-wheel self-levelling suspension system, complete with steering column adjustment rod which changes ride height in real time.
This stuff does not come cheap. Then again, nothing worthwhile ever does.
My 1979-built example was first registered on 1 January 1980 and is number 7,224 of 7,380 examples produced – a very low production run by post-war Mercedes standards.
It is finished in Thistle Green over Brazil brown leather interior, runs a Becker Europa and is sans sunroof – an advantage in restoration terms.
With just 70,000 warranted original miles and an engine rebuild in store with a noted marque specialist, the car is sure to continue making the sort of Germanic horsepower that inspired a generation of petrolheads who were seeking the ultimate post-war expression of Mercedes-Benz muscle cars.
A precursor in some ways to modern AMG models, the 6.9 is in cubic inches greater than anything that has succeeded it: and in fact greater than any American passenger models at its culmination of production in 1980.
To drive, a 6.9 is part-muscle car, part-technological marvel, and plain old just great fun. It will shred the tyres at any speed in any conditions resembling rain and it will approach 110mph in second gear.
In the dry, you will achieve wheelspin on the downshift from third to second gear yet the car would not provoke this without manual inputs, proving that it still adheres to the time-honoured Mercedes dual personality of massive power but only on strict command.
You will never accidentally find yourself in a hedge, put it that way.
But where the 6.9 distinguishes itself from other fast saloon cars – say the Maserati Quattroporte or the Aston-Martin Lagonda – is that you can really make it work for a living, putting out big power all day and then easing off without any discernible change in the car’s emotional state.
This is not the case with other marques where the componentry will simply give up and go home after a while. The 6.9 was designed to do 120mph plus for long periods and this is evident in how the drivetrain relaxes you through those long stretches.
Fuel economy isn’t its strong point (a Silver Cloud V8 is more frugal) but as already mentioned, nothing worthwhile ever comes without a price. Where a John Blatchley-styled Cloud is probably the ultimate stylistic interpretation of a four door saloon car, the 6.9 is the ultimate engineer’s example. Intriguingly the production cycle for both cars was only 9 years apart – a testament to just how good cars were in the 1960s and 70s.
The self-levelling suspension on all four corners was also not without its complications and Mercedes wisely made this an option rather than standard fitment on the later W126 model which mostly got by with coil springs and the occasional self-levelling specification on the rear axle.
However, in 1974, to deal with the enormous weight transfer dictated by the large engine and its capable top speed, it was certainly a more reliable engineering solution than its predecessor on the 300SEL 6.3 – air suspension. And a good deal safer than the strongest available coil springs at the time without compromising ride quality.
A 6.3 is still a fantastic car, the real genesis of Mercedes’ power saloons, but a properly sorted 6.9 is bigger, faster, better handling and in many ways the ultimate interpretation of Mercedes’ most creative engineers until the W140 was launched in 1991.
The 6.3 was never intended to power a regular production saloon whereas the 6.9 was built from the ground up with its specialist engine in mind. This engine never appeared in any other Mercedes car, unlike the earlier 6.3 which also powered the W100 600 Grosser, for which it was originally designed.
Interestingly both 6.3 and 6.9-litre engines carry the internal designation M100 but both are entirely different and no single part crosses over between the two. The 6.9 was the only W116 S-Class model to receive walnut interior trim and alloy road wheels as standard (for brake ventilation, not style reasons, of course) but customers were still required to option a passenger door mirror and radios were dealer-fitted accessories in that period.