Mercedes-Benz used same engine numbers M117.982 (D-Jetronic) and M117.985 (K-Jetronic) to deliver different engine versions for Europe / standard, the USA (emission regulated) and low compression (NV= niederverdichtet) markets with lower fuel quality both in 450SL and 450SLC as well as with other numbers in W108 280 SE(L) 4.5 and W116 450SE . But in reality these are very different engines that vary in compression, power, torque, cam shaft and emission control a lot.

The following table tries to give an overview over 450SL and 450SLC engines. 90% of all 450SL were built with US engines, so don't be surprised to normally find them in all the 450SL reimported to Europe from the US. The 450 engine at first was only available in the US while Europe got the smaller 350 engine with a similar power. Only as of 1973 MB delivered a more powerful European 450 engine. Unfortunately it is really difficult to identify which kind of engine is built into a car. Neither cam shafts nor the absence of exhaust return valve or the presence of European Jetronic and ignition components can make you really sure about the version as everything could have been swapped. In doubt only a compression test can give such a hint.

Compression ratio is done by different pistons. Main shaft is identical.

According to EPC cam shafts are changed more often than shown here.

Sources: Engelen, Wikipedia, EPC