The Pertronix setup will not change plug performace if you only replace the points and use the original coil. If you use the replacement high voltage coil, you can open up the plug gap to whatever they recommend. You should also replace the plug wires if you change the coil as the old ones may not hold up well to the increased voltage.

Heat range should be as specified by Benz unless you find you need a higher or lower range to prevent fouling or plug overheating. The exact performace of your carbs will have an effect, too, as it's very difficult to get them to give exact mixture control all the time.

If you have problems with carbon fouling and you KNOW you aren't running rich, use a hotter plug. If the insulators blister on the tips while staying brown at the base, you need a cooler plug.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!