I recently saw a profile of the 189 combustion chamber...offset to one side with the spark plug located on the side of the block, cylinder head/block interface at an oblique angle.
Given that it has been known for a long time that a hemispherical combustion chamber is ideal, I can't understand how Mercedes' engineers came up with this peculiar design, which was not in fact very efficient. It took other exceptional measures...long ram tubes, fuel injection, free flow exhaust and high compression... to get respectible power out of this engine in the SL application (actually about 180hp, not the 215+ that was claimed).

Is there anybody that can shed any light on Mercedes' thinking regarding the design of the 189 cylinder head/combustion chamber?

P.S. I know from recorded comments by Rudolph Ulenhaut that Mercedes' engineers had to "make do" with existing 300 sedan components in creating the 300SL, which means that the 189 engine design was intended for a sedate sedan rather than a sports car, but the question remains, why was the chosen design considered good for THAT application?

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Berfinroy in CT
Present vehicles:
1973 300 SEL 4.5
1959 Rolls Royce Silver Cloud I
1973 Citroen DS23 EI five speed
Past vehicles;
1959 Thunderbird convertible/430
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