Thermo vacuum valve/switch color/temperature

[mbboy]

The ears of the two, red-top, thermo-vacuum valves on the intake manifold of an 81 380sl I'm rebuilding broke off when I tried to remove them, and I'm trying to figure out whether to replace them with the original, red ones, which open at 50 degrees, or yellow ones, which open at 70 degrees.

The CD states "the acceleration enrichment is controlled in dependence of a vacuum at a coolant temperature below 50 degrees C (70 C starting August 1984)," but the parts guy at the local dealer shows the 70 degree valve for the 81, too.

OTOH, various websites still show the 50 degree valve for the 81, or ask for the color to be specified when ordering, and the Performance Products catalog shows that both version were still being used on the 560.

So I was wondering if anybody here happens to know what the pros and cons of using the 70 vs 50 degree valve is, and why MB decided to use the higher temperature valve in the 84-85. Thanks in advance for any info .