Welcome to the Hooniverse Obscure Muscle Car Garage, a regular feature which aims to expand the notion of what a muscle car is, and to see if there’s room in the muscle car universe for a German sedan. This is the second Mercedes Benz über-sedan that I have profiled in this series, and I think it was the better of the two. So, let’s take a look at what happens when you take a standard, everyday German Sedan, stuff a huge engine under the hood from what is essentially a large limousine, and bring it to a performance-hungry market. Introducing the Mercedes Benz 300SEL 6.3

The 300SEL 6.3 model was introduced in the United States in June 1968, quite appropriately at the Laguna Seca race course, with famed 300 SL designer, Rudolf Uhlenhaut in attendance. He pointed out that the car had better road-holding ability, braking potential, suspension stability, and maneuverability than any comparable automobile in the world. It had first been shown in Europe in March 1968.

With the 6.3 Liter fuel-injected 300-horsepower V8 engine installed in the slightly modified but outwardly regular sedan body of the New Generation type, the car weighed 3,835 pounds and had a power-to-weight ratio of 12.8 pounds per horsepower. Performance was truly fantastic, especially when Herr Uhlenhaut demonstrated the car’s abilities.

The sedan had the air suspension of the 600 series and many extra features were included as standard items, such as air conditioning, radio, leather upholstery, power steering, and power windows. Except for the “6.3″ badging on the trunk lid, the car was not distinguishable from the regular 300SEL model.

After exhaustively testing the car, Road & Track magazine called it “the greatest sedan in the world,” stating that the 6.3 was “truly the executive road racer … does more different things well than any other single car.”

Reports of performance varied tremendously, depending on the car’s age and how it was broken in. Mercedes cars of this vintage were largely hand assembled, which also added to the varibility. Regardless of the real numbers, the car was clearly unique in its day, and had no rival

It’s possible to get even more performance out of these cars. There are simple bolt-ons available from experienced Mercedes shops that will get you up to 350 SAE net HP and improve the driveability and acceleration times.

It takes enormous amounts of horsepower to get the car over about 150 miles per hour because of its antique, boxy shape, so most current owners are making improvements for the sake of reliability and maintenance, not more horses.

The car magazines loved the big engined Mercedes 300 SEL 6.3, and they couldn’t wait to test its speed. Motor Trend in June 1968, Road & Track in June and November 1968 and August 1971, Car and Driver in October 1969, and Road Test in 1971 all tested the Mercedes hot rod. Remember that its test numbers were established on skinny 195-70-14 inch tires that went up in smoke when you applied the 437 ft/lbs of torque. It’s all too easy to lay rubber the the first 2 gears of the 4 speed automatic. Remember the typical American Muscle car had 3.73 rear in gears, the 6.3 would be close to 5 seconds flat 0-60 mph with 2.85 gearing. So you’re asking, what kind of performance was wrung out of the 1968 300SEL 6.3? How about 1/4 Mile times of 14.4, at a speed of a little under 98 MPH. Top speed? That would be 141 MPH, and that’s with a curb weight of 4,000 pounds.

There were over 6,500 300SEL 6.3′s produced between 1968 and 1972, which was the last year for the W109 Body Style. US Sales were almost 1,840 for the same time period, or a little over 28% of the total. So, we have this rather rare, very fast, 4-door sedan with a huge 6.3L V8 under the hood. Is this an Obscure Muscle Car, and should it be on the Garage, or is it just a well-behaved carriage that should be pampered and kept in a collection?

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