Can you please explain to me why some of the MB engines have less horsepower than other engines, but have greater displacement.

Example the early 80s 380 SEL had 155 hp

the 90 300 SEL had 177 hp..


Also the 420 SEL had more hp than the 500 SEL.

Was wondering what made up for the difference

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'89 420 SEL
'90 300 SEL
'68 Olds 88 Convertible
'84 300 SD (sold it)