Under the hood, the BMW packs a powerful punch. An S38 inline-six engine from a BMW M5 E34 replaces the original engine, delivering 311 horsepower compared to the original 180 hp. However ...

In 1986, BMW introduced a second version of the M635CSi fitted with an S38-series unit rated at 256 horsepower and 243 pound-feet (330 Nm) of twist. The M6 arrived in 1986 as a US-only model and ...