Mercedes-Benz 300 SEL 6.3: Ride of the Valkyries

by James Kraus

Stuttgart Express: The 300 SEL 6.3 at speed

The legendary and storied Mercedes 300 SEL 6.3 was a seminal automotive creation of the 1960’s; a comfortable, quiet, soft-riding, full-featured and meticulously crafted sedan that went like a Ferrari. Nothing quite like it had ever come along before.

The W108/109 S-Klasse Mercedes that served as the basis for the 6.3 was actually the first iteration of the S-Klasse as we know it today. Prior to its debut, The S models of the Ponton and Fintail era were simply mid-range models with longer front-ends, larger engines and superior trim.

The new S-Klasse, 1965

The new S was introduced at the Frankfurt Auto Show in September, 1965. Its chassis was based on the Fintail drivetrain, suspension and platform architecture with an all-new body and interior. The new body design was one of the last from the era I like to think of as Mercedes’ Elegant period, though signs of the later Functional period appear for the first time in the form of the discrete rubber strips adorning the bumpers and beltline mouldings. The S-Klasse styling bore elements from both the 230 SL and 600, each introduced two years earlier, with simple, taught lines and generous glass area. The roof was nearly flat, hinting toward the concavity of the SL’s removable “Pagoda” hardtop.

300 SEL front view

Its most stylish aspect was the frontal view. Here the classic M-B multi-function bubble headlamp lenses were given considerable forward rake like the prow of a ship, acting as a keen counterpoint to the rearward tilt of the radiator grille. Together, these two elegantly simple elements combined to bestow a proud countenance appropriate to a high-ranking Mercedes-Benz.

The range-topping 300 SEL was a fully contemporary, roomy and luxurious conveyance with four-wheel disc brakes and fully independent self-leveling air suspension. Its only shortcoming was that the power developed by the 3.0-litre engine was not up to the task of fully exploiting the sophisticated chassis.

A mid-size V8 was in development to address this issue, but it was still a few years away from production. In the interim, Erich “Wax’l” Waxenberger of the Test and Development department at Mercedes-Benz trial-fitted the massive 6.3-litre V8 from the flagship 600 into a 300 SEL. Famed development chief (and former competitions department head) Rudolph Uhlenhaut took the modified car for a drive, championed the idea of developing the concept for production and secured management approval for production of the 6.3-powered S-Klasse.

Mercedes-Benz 6.3-litre V8 as fitted to the 300 SEL 6.3 (distinguished by the single-alternator and low-mounted a/c compressor)

The new 300 SEL 6.3 debuted at the Salon de Genève in March of 1968. Changes to the standard 300 SEL were minimal. Wheels of a half-inch greater width (6.5-14) were fitted with larger 195/70-14 V-rated tires, ventilated brake rotors were added front and rear and the fuel tank was enlarged. Finally, a tachometer was fitted to the centre of the instrument cluster, displacing the clock. To replace the evicted timepiece, engineers dipped into the parts bin to borrow the rectangular unit from the W111 Coupé, which fitted nicely into the instrument panel to the left of the steering column.

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View from the bridge

The final modification was a mixed blessing: in order to take advantage of the very latest headlamp technology without the delay of creating production tooling for modified lamp units, the graceful front lamp clusters were abandoned in favour of blunt-faced over-and-under circular lamp units using newly introduced quartz-halogen H1 bulbs. These were simply plugged into the mounting cradles and bezels heretofore used to mount standard sealed-beam lamps for the U.S. market. Better lighting performance was achieved, but at rather steep cost in terms of frontal aesthetics.

The 6.3 came standard with the DB 4-speed automatic gearbox, but at least one was built with a ZF 5-speed manual transmission. All but the earliest models had a limited-slip differential fitted, which was available with three different final-drive ratios: the standard 2.85 and more accelerative 3.69 and 3.92 options. As with all Mercedes models (except the 600), the new M-B light-alloy road wheel became an available option in April of 1970. Another available upgrade was the classic M-B ivory steering wheel, which today adds an extra dose of period character to a number of surviving 6.3’s.

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Publicity Photo, 1968

The motoring press blanketed the 6.3 with accolades. A quote from Road & Track is typical: Its 6.3-liter V-8 gives it the acceleration of the Porsche, its air suspension gives it a ride equal to that of the Jaguar XJ6 and the handling (at least in expert hands) is almost as good as that of the Ferrari 365GTB/4. And yet it is the roomiest and most practical car of the group. If we had to choose one car, regardless of cost, to serve all our automotive desires, it would have to be the 300 SEL 6.3.

To understand to impact of the 6.3, consider for a moment that the new model boasted a 70% increase in power and no less than a 100% increase in torque over the 300 SEL, the previous top-line S-Klasse variant. To put those numbers in perspective, the current AMG models have an advantage over their standard S-Klasse brethren of at most 40% in power and 51% in torque output.

The most recognizable view of the 6.3

What is important to note here is that the 6.3 enjoyed the same cosseting ride and the same low noise level as the standard 300 SEL. And it looked identical apart from the single 6.3 emblem at the rear. If the Nomenclature Delete option was specified, the 6.3 was virtually indistinguishable from any other long-wheelbase S-Klasse Mercedes-Benz. One of the great attributes of the 6.3 was stealth. It revealed nothing and telegraphed no warning of what lay beneath.

Compare that to today’s 6.3 models embellished with stylized wheels, a plethora of badges, aggressive front and rear fascias, a phalanx of outsized exhaust embellishers and other accoutrements to announce their presence with all the subtlety of musical air-horns playing La Cucaracha.

The 300 SEL 6.3 in contrast was a true gentleman’s express. Unlike the flamboyant models of today, the original 6.3 went about its business rapidly, but also quietly and unobtrusively.

The sole giveaway

The sole giveaway

Consider the following quotes from the November 1968 issue of Road & Track in regard to the 6.3:

The styling is conservative; there isn’t a frill or a furbelow anywhere…

Inside, it’s luxurious but not oppressively so…

Everything has the air of unostentatious good taste…

Mercedes hasn’t made the mistake of forgetting that they’re building an automobile and that automobiles are for driving, not womb-substitutes or ladies’ powder rooms…

It is quite sad that unfortunately, none of these statements can be made today in regard to current production Mercedes-Benz automobiles. While Audi and BMW sedans still adhere (to some degree) to the simple, handsome functionalism that was once the hallmark of German design, Mercedes seems to have lost the script.

The illustrious 300 SEL 6.3 passed into history when the W109 S-Klasse was replaced by the W116 series. It was revived as the 6.9 in 1975, but the 6.9 never captured the imagination of enthusiasts as did the original 6.3. In the most part this was because the 6.9 could not match the comparative dynamic advantage of the 6.3 over its contemporaries, given that the performance of many other cars increased significantly in the intervening years.

As an illustration, upon its introduction in 1968 the 6.3 could run with a contemporary top-range Porsche 2.0 911S, even out-accelerating the Porsche below 100 km/h. In 1975 however, both the Porsche Turbo and 2.7 911S were capable of outpacing the newly-launched 6.9.

The 300 SEL 6.3 was available for only four-and-a-half years, but it has left a rich and lasting legacy among automotive cognoscenti. There had been nothing comparable before, and nothing really similar since. The difference in the performance envelope between a 6.3 and other sedans (and most cars of any sort) in 1968 was an order of magnitude. The difference today between the S65 AMG (which some would consider a spiritual descendant of the 6.3) and many other models both in and outside the Mercedes-Benz family can sometimes be expressed in just a few tenths of a second.

For period road tests and other information on the 300 SEL 6.3, visit the 6.3 Page of The International M-100 Group 

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5 thoughts on “Mercedes-Benz 300 SEL 6.3: Ride of the Valkyries

  1. We share the same taste! I too prefer the original W109 headlamps over the “4-eye” setup of the 6.3. Luckily, technology has come to the rescue with the dual-filament H4 halogen lamp which is now available with the original bi-lux P45t base. This drops right into the original W109 “bubble” lamp fixture and gives the same output as the H1 lamps originally installed in the 6.3. This is what I have on my personal 6.3 at present.

  2. I recall the 300SEL 6.3 taking journalists by complete surprise when it showed up at Geneva as development of the car was successfully done in complete secrecy, and Mercedes had made no pre-show announcement.

    The 6.3 was definitely one of the greats of the late ’60’s

  3. I can certainly attest to the inadequacy of the 3.0L engine first installed in the W108/109. For a few years when I was very young and far too poor to support the project, I nursed a spectacular-looking (but in reality very rusty) 1967 300SEL along its way to the junkyard. Positive: it had the elegant bubble headlights. Negative: everything else.

    One of the motivations for Uhlenhaut’s approval of the M100 transplant must have been a great desire to simply bury the 3.0L. It is to his everlasting credit that he signed on to the Nuclear Option!

  4. Have owned a 6.3 since 1976. Still own the beast. Still in love. What a car! Slightly modified, there is no other. It goes out weekly to our local car club events in the summer.

  5. I’m looking for one to accompany my ’92 500E and my ’06 S55 in the stable, both of which are spiritual descendants to the “wolf in sheep’s clothing” ethos of the 6.3.

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