M9456

Porsche's larger 1924 six followed the same recipe as its 3.9-liter sister — vertical-shaft overhead camshaft, cast-iron head, iron liners in a light-alloy block — stretched to 6.2 liters and fitted with an engageable Roots supercharger taken from the racing department: 100 PS on the carburetor, 140 with the blower in. The number is a description rather than a name, 90 mm bore and 145 mm stroke across six cylinders. It succeeded the 28/95 PS at the head of the range, and from February 1925 the two supercharged sixes were the only Mercedes passenger cars in the joint sales program with Benz & Cie.

Early in 1926 came the K — kurzer Radstand — with 350 mm out of the wheelbase, compression raised to 5.0, and battery ignition feeding a second set of plugs. Otto Merz, Rudolf Caracciola and Christian Werner took the first three places in the twelve-hour touring car race at San Sebastián that year. Renamed Typ 630 in 1928, the model ran to 1,033 standard cars and 150 short-chassis Ks. Bored out to 6.6 and 6.8 liters, the same design kept racing into the early 1930s and gave the S series its starting point.