Featured: Mercedes-Benz 450SEL 6.9 Was All About Engineering

Mercedes-Benz 450SEL 6.9 Was All About Engineering

By Ronald Ahrens
November 4, 2016
12 comments

Editor’s note: This article originally appeared on Sept 30, 2014, we’ll be diving into our archives to bring you some of the gold you might have missed from our early days.

Photography by Rémi Dargegen

It is hardly possible to overstate the grimness that prevailed thirty-seven years ago when the 1977 Mercedes-Benz 450SEL 6.9 came the United States. The nation seemed to be inextricably in OPEC’s grip, the so-called federalizing of automobiles was in full swing, and John DeLorean was just revealing his strange sports car as The Answer. Even worse, K.C. and the Sunshine Band kept singing “I’m Your Boogie Man.”

Yet going back even beyond Nixonian times, the horsepower wars being fought in Detroit had captivated the Germans. The Mercedes-Benz 300SEL 6.3, made from 1968 to 1972, was engorged with the V-8 from the 600 limousine, becoming the grandfather of all the German sports sedans. Meanwhile, in the five years between its discontinuation and the appearance of this new sedan, emissions controls were choking carbureted cars. Even the Chevrolet Corvette was hitting singles instead of home runs.

Just in time, the world’s fastest production four-door sedan dropped by to say guten tag for $38,230, an outrageously expensive price for a car that someone like Mr. Lee Iacocca would have condemned for its lack of velour. It had hard leather seats, a godawful slab of wood on the dash, and few other amenities. Slightly wider fourteen-inch wheels and a 6.9 emblem on the trunk lid distinguished it from the garden-variety 450SEL. What you were paying for wasn’t flash, it was engineering. And the engineering started under the hood.

A few large American sedans had big-block engines before new emissions regulations pretty much killed them off, but nothing was as sophisticated as the hand-built SOHC 6.9-liter V-8 in the 17.5-foot-long Mercedes’s engine bay. The displacement was achieved by boring out the 6.3-liter engine to 6834 cc. Mechanical fuel injection helped with U.S. certification, although at 10 mpg in the city and 14 mpg on the highway, efficiency could never be claimed. To aid with packaging and maintain the low hood line, the V-8 had a dry sump. The oil reservoir in the right-front corner held the 12.7 quarts necessary to satisfy internal flow requirements; an incidental benefit was the oil change interval of 12,500 miles or once a year, whichever came first.

Other sophisticated touches included the engine’s aluminum cylinder heads in an era when cast-iron still ruled. Sodium-filled exhaust valves encouraged heat dispersion. This was neither a high-compression V-8 at 8.0:1, nor a high-revving one: it generated 250 hp at 4000 rpm and redlined at 5000 rpm. Torque output of 360 lb-ft made itself felt at 2500 rpm. (Horsepower and torque were about 12- and 11-percent reduced from the European version.) A three-speed automatic transmission brusquely managed the torque, sending it via a limited-slip differential to the rear wheels. Dashing from 0 to 60 mph required 7.1 seconds, and top speed was 133 mph.

The engineers also devoted themselves to ride and handling, so the 6.9 was outfitted with a hydropneumatic suspension that compensated when the accelerator or brake pedal got stomped. Oil was pumped in and out of a strut at each corner, as required to meet variations in load, and this hydraulic action combined with a stored supply of nitrogen to effect damping and springing; the self-leveling was a related benefit for the 4390-pound car. Stiffer front and rear stabilizer bars countered body roll.

Electronic controls for the powertrain, suspension, and chassis were for the future. Meantime, the 450SEL 6.9 represented the high-water mark for purely mechanical efforts to motivate and regulate a big beast. In his thorough review for Car and Driver, Mr. David E. Davis, Jr. noted the complexities and imperfections but called the car “an exclamation point on the story of an entire automotive era.” Given the bleakness of the time, Davis certainly could not be blamed for failing to foresee such amazements as the BMW 740i and 750i, which would come in a generation. All he knew was, whereas the 300SEL 6.3 had creaked, the 450SEL 6.9 crowed.

Now one of the most highly prized and collectible sport sedans ever, the 6.9 was manufactured until 1981, and a substantial number of the 7380 units have ended up in the U.S. Buying one doesn’t require an arm and a leg, as the very best examples don’t generally crack the $50,000 barrier. Besides cash, all the buyer will need is the number of a good mechanic.

Thank you to Montfort Automobiles for allowing us to photograph their Mercedes-Benz.

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12 Comments on "Mercedes-Benz 450SEL 6.9 Was All About Engineering"

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Jim Levitt
Jim Levitt

6.3s were faster and more fun to drive.
I owned two including the last 1971 sold in CA.
I think I sold that one around 1976 and so I went to test drive a 6.9 and was thoroughly disappointed. It was slow and sluggish off the line and didn’t have the classy interior of the last generation.
(I never bought one).

waltzieg
waltzieg

I’m 52 years old. My father had achieved a second hand 450SEL 6.9, bordeaux with beige velours interiors, I think in 1978. I remember the sensational sense of luxury and confort, flying low at high speeds in the empty highways of the Spain of that time.

waltzieg
waltzieg

My father was both german, and engineer. He was proud of that car, even if he told me that, during a journey to the Basque country, has had to do 60 km on reverse, because automatic gear was blocked!

Majed Mougharbel
Majed Mougharbel

In Europe and the Middle East, to my knowledge and if memory serves me right, the 450SEL 6.9 was the first car to be limited to 250 kph (155mph).

marco Uchello
marco Uchello

“Just in time, the world’s fastest production four-door sedan dropped by to say guten tag” I thought the Australian Falcon GT was the fastest 4 door production car at this time with 141MPH just in time to say G,Day

Stig Schumacher
Stig Schumacher

Sadly many were exported to the USA with ugly bumpers headlights and most of all detuned engine, most likely Euro 4.5 V8 would easily overtake it and not to mention they were driving them at 55mph over there lol

Jim Levitt
Jim Levitt

ALL (not many)!

MGB GT 72
MGB GT 72

My granddad had the predecessor (W108 280S) and this one the W112 280SE both new. I remember being a small boy with my dad and grandad checking the > 200km/h topspeed of the new 280 SE in 1973. (we live in the Netherlands)

Later on my dad owned a MB W201 190D, a W124 300E and a W1124 250D. Nowadays he drives a W204 200cdi estate.

I tried not to drive Mercedes having driven only new BMW’s and Audi’s, but I must say I like the new E class estate, I am certainly considering it. …….The circle closes eventually????

Alexander Shaghoury
Alexander Shaghoury

Great car and pics, but I have to disagree with one statement. In my opinion, by saying ‘flash’ wasn’t a thing you’re actually missing the point. Just as any other w116 or upper range w123 it had very significant number of options and comforts for its time. And a funny part about ‘lack of velour’ as velour sits and door panels were quite a popular option – they can be found just as often as leather, cloth or mb-tex.

Yoav Gilad
Yoav Gilad

That’s because Mr. Lee Iacocca (head of Chrysler at the time) was probably promoting the velour-optioned 450SEL on the side… 😉

Dustin Rittle
Dustin Rittle

I must admit i was never a huge fan of MB cars but after reading this article and seeing this car i have to say im starting to change my mind. Thanks again for the lovely picture.

Giancarlo
Giancarlo

Would be nice a challenge with the 300 SEL 6.3 😉

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