300SEL 6.3

The 6.3 Story

The Mercedes-Benz 300SEL 6.3 is a full-sized luxury performance sedan built by Mercedes-Benz from 1968 to 1972. It featured the powerful 6.3-litre M100 V-8 from the top-of-the-line flagship 600 limousine. Up to this point, Mercedes did not put V-8 engines in any other product line but the W100 Limo. All the other 300 Series Sedans, Coupes and Convertibles received the 3.0 liter, 6 cylinder, fuel injected motor. Also remember this is 1968, the heart of the muscle car era in the US. Mercedes was selling into the American luxury market and all their competition came to the game with V-8 engines, some in excess of 400hp.

How did this come about? The same way Jim Wanger secretly built the prototype for the Pontiac GTO, and a little by accident you might say.

An engineer at Mercedes named Eric Waxenberger ended up with a 300 series car that had been damaged on the production line, so it was sent to the engineering as a test mule. He magically also procured an M100 engine and transmission. With a couple of his staff, he worked after hours so as not to be noticed and they did the heart transplant and started to test it on the grounds of the factory. It was instant gratification! They knew they had a monster on their hands, but they were soon found out.

Eric’s boss was working late one night and heard the car circulating on the test track. He instantly knew something was totally different about the sound. He went down and started asking questions!  Fortunately, that man was Chief of Engineering, Rudolf Uhlenhaut. Uhlenhaut was responsible for all the major post war Mercedes racing successes and created the iconic 300SLR, and the W196 Grand Prix Cars.   He immediately insisted on a test drive in the new package and was so impressed he went to the MB Board within a week to propose production of this combination. The board thought they may only sell several hundred of this model but approved it in the end. When production was halted, a total of 6,526 300 SEL 6.3s were produced, out selling the 6-cylinder model in the product line. The result was a nearly 2-ton luxury sports sedan with muscle car performance, the fastest sedan in the world for several years.    

The company introduced the 300SEL 6.3 at the 1968 Geneva Motor Show and it was an instant hit. The 6.3 greatly enhanced Mercedes-Benz’s reputation for performance vehicles, languishing since the end of production of the Iconic 300SL Gullwing and 300SL Roadsters of the 1950s. It also made better use of the M100 engine production facilities and offset the development costs of that motor. By the end of line’s production, the 6,500 built for the 300 SEL 6.3 far outnumbered the 2,700 engines turned out for the 600.

 M100 engine in a 300 SEL 6.3

The 6.3 could cruise at over 200 km/h (124 mph) with five occupants in complete comfort. This also led to the expansion of V-8 engine option in other model lines. The 3.5- and 4.5-liter V-8 engines were developed, and that design was expanded and used all the way up into the 90’s ending with 5.0- and 5.6-liter powered cars. V-8’s was now available in sedans, coupes, convertibles, and the SL Roadster.

In 1972, the 109 model 300SEL was replaced by the W116 S-Class model. The 116 came initially with the M110 6 cylinder, the 3.5 or 4.5 V-8 and the turbo diesel, but no M100 powered version was available until 1975. The Mercedes-Benz 450SEL 6.9 was introduced as a 300 SEL 6.3 successor with a larger displacement engine for more power and various modifications to the equipment including a dry-sump lubrication system. Along with that came a much larger car and a heavier car too. A car that would never be as nimble and sporty handling as the 6.3.

The 300 SEL 6.3 was an extremely luxurious vehicle for its era. Standard features included air suspension, ventilated 4-wheel power disc brakes, power windows, central locking, and power steering. Air conditioning, power sunroof, audio tape deck, and rear window curtains, writing tables, and reading lamps were available as options.

Enjoy these YouTube videos on the 6.3

1972 Mercedes-Benz 300 SEL 6.3 – Jay Leno’s Garage – YouTube

The Mercedes 300 SEL 6.3 Invented an Entire Genre of Car — BTS with DTS — Ep. 9 (youtube.com)

Engine Specifications

• 6.3-litre V-8 with Bosch Mechanical Fuel Injection,
• 247 hp at 4000 rpm,
• 369.0 lb⋅ft of torque at 2800 rpm, peaking at 434 lb⋅ft .
• Max. engine speed: 5250 rpm

Performance

• 0-62 mph (100 km/h): 6.6 seconds
• 0-100 mph (160 km/h) : 14.6 seconds
• Standing quarter mile: 14.2 seconds
• Top speed: 137 mph (factory figure)

Just how fast was that?  Compare this with other cars with the same performance from that era.

1965 Chevrolet Chevelle Malibu SS 396 Z16                     0-60 mph 6.7    Quarter mile 15.3

1967 Chevrolet Camaro Z/28 RS                                             0-60 mph 6.7    Quarter mile 14.9 

1968-69 Chevrolet Camaro SS 396                                         0-60 mph 6.6    Quarter mile 15.0 

1971 Chevrolet Corvette Stingray 350 LT-1                         0-60 mph 6.0    Quarter mile 14.6

1965 Ferrari 330 GT Series I                                                     0-60 mph 6.3    Quarter mile 14.6 

1967 Ferrari 275 GTS/4 NART Spyder                                    0-60 mph 6.7    Quarter mile 14.7

1968 Ford Mustang GT 390                                                     0-60 mph 6.3    Quarter mile 14.8 

1970 Ford Mustang Boss 302                                                   0-60 mph 6.1    Quarter mile 14.6

1970 Plymouth Hemi Cuda                                                       0-60 mph 6.3    Quarter mile 13.9

1968 Pontiac GTO 400 Ram Air (Manual)                            0-60 mph 6.8    Quarter mile 14.3 

1969 Pontiac Grand Prix 428 H.O.                                          0-60 mph 6.8    Quarter mile 14.5 

1969 Pontiac GTO Judge                                                           0-60 mph 6.4    Quarter mile 13.9 

1969 Pontiac Firebird Trans Am 400 (Manual)   0-60 mph 6.5    Quarter mile 14.9

1969 Porsche 911 S                                                                   0-60 mph 6.5    Quarter mile 15.1 

1972 Porsche 911 T                                                                   0-60 mph 6.9    Quarter mile 15.1

1966 Shelby GT350 Mustang                                                    0-60 mph 6.9    Quarter mile 15.1 

1967 Shelby GT500 Mustang (Auto)                                       0-60 mph 6.5    Quarter mile 15.0

The 6.3 in Motor Racing

Eric Waxenberger was also a natural in a race car and wanted to campaign the 6.3 in several different events. He built several racing versions and started to campaign them with no outward connection to Merecedes-Benz, trying to stay under the radar of the Factory Management which prohibited this activity. The cars were very successful, and it could no longer be hidden as to who was involved.

At that point the cars and the racing program was turned over to two ex-Mercedes engineers who had left the company to form what is now known as AMG. They were already in the business of tuning Mercedes-Benz for higher performance including the 6.3, so it was a natural transition.

AMG further modified the 6.3 sedan to compete in racing events and nicknamed it the “Red Sow” or” Red Pig”. AMG bored it to 6.8 liters and yielded 422 hp. Its most famous for being entered in the 24 Hours of Spa Race in 1971, and finishing second overall, beating all the top sports cars of the day. If not for poor fuel mileage and tires that could not handle the weight and horsepower, it would have won. It put AMG on the map and eventually AMG became the high-performance division of Mercedes-Benz. To this day the 300SEL 6.3 and the “Red Pig” are true icons to the brand and the collector market. Mercedes-Benz brand DNA and their racing history would not be the same without them.  

Mercedes-AMG: Milestones – Episode 1: 1971 (youtube.com)

AMG 300 SEL 6.8 at the 1971 Spa-Francorchamps 24 hours (youtube.com)