FONZI: The horsepower figures you cite are the generally published ones for a "stock" car, although it should be noted that different states of tune were available. This was a limited production exotic car, after all.
That being said, it should also be noted that the 1958 300 series of sedans (the D Adenauer, S roadster and SC Cabriolet) had the same basic M189 fuel injected engine that were rated at 160 hp, and even with longer intake runners, higher compression ratio (although still only 8.5) and more aggressive cam, its a long way from 160 to 212, let alone 240. The 180 hp figure I suggested cam from an episode of Jay Leno's garage, wherein his shop rebuilt a 300SL engine and could only get 180 on their dyno. He called a number of 300SL experts to find out why, and was told that 180 was in fact the real number!

T WALGAMUTH. Yes, torque is another thing, but is much harder to come by than horsepower. More displacement or forced induction are pretty much the only way significantly more of it. The M189 3 liter in the 300SL that is generally said to have 212 HP is said to have 203 ftlb of torque, which is about all you are going to get out of a naturally aspirated 3 liter, which did benefit from "ram" intake manifolds. That doesn't seem like enough to get a 2851 lb car with a cd of .38 (very good for the day) up to 150+.....

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Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1959 Ford Thunderbird convertible/430
Past vehicles;
1958 Bentley S 1
1976 ex-Max Hoffman 6.9
1970 300SEL 2.8
1958 Jaguar MK IX
1961 Jaguar MK IX
1963 Jaguar E-type factory special roadster
1948 Plymouth woody
1955 Morgan plus 4
1966 Shelby GT350H Mustang