The decade of the 1980's dawned with numerous challenges in the worldwide automotive industries. Unique challenges such as emissions, fuel economy, and safety presented problems to all makers of autos in the early 1980's - changes that auto corporations were not prepared to address.
Because of catalytic converters, air pumps, EGR valves, and detuning engines, the U. S. Mercedes performance woefully lagged that of its European cousin. In 1981 the 3.8 litre V-8 engine debuted in the U. S., and they were installed in the 380SL and the 380SEL models. The new 3.8 litre engine was presented with an all aluminum block to replace the cast iron block of the 4.5 litre engine. The rest of the design was basically the same: overhead cams, CIS fuel injection with Lambda, which includes an oxygen sensor to help with fuel trim. The one glaring difference was the single row timing chain. The Mercedes European counterpart 3.8 litre engines retained the double row chain and gears from the 4.5 litre engines and the only reason for the single row chain appears to be weight related. But how much weight? Maybe 2 lbs for a chain, 2 cam gears, an intermediate gear, and a gear on the camshaft.
The result of this application was somewhat immediate, as far as the failure of the single row chain. Mercedes blamed this on "poor maintenance," and did convert some to the double row chains for its "good" customers. Making the transition today to the double row set up is expensive ($3000) because the timing cover needs to come off and not only does the chain need to be replaced, but the cam gears, the idler, and the crank gear, and possibly some of the rails. The single row timing chain continued in the U.S. through 1983. In 1984 the single row chain was replaced with the double row chain and double row gears.
Today, most of the conversions, especially on the 380SL, have been performed, but occasionally a single row chain does appear. If I were presented with a single row chain 380SL, I would recommend that the chain be replaced every 25,000 miles (about $300) and that the oil be changed every 3500 miles.
With this being said, I still cannot find the reason Mercedes Benz would use the single row chain in 1981. From a quality performance engineering and financial point of view, it makes no sense. If any of our readers have any input, it would be appreciated to solve this mystery.