The BBB gives directions for connecting dwell meters on transistorized ignition cars, but the connections depend on the meter used. Some, but not all, of the connections are listed below. (BTW, these directions do not apply to types 108.067, 108.068 and 109.057).
For SUN engine testers WITHOUT change-over switch for transistorized Coil Ignition Systems -
RPM/dwell angle testers TDT 5,6, 12, 216:
Red clip to outlet of 0.4 ohm series resistor (two outgoing cables at outlet).
Black clip to inlet of 0.6 ohm series resistor (resistor between switching unit and ignition coil).
Note that other testers are also listed which seem to have more connections, so I'm guessing they are the bigger testers that shops of that era would have had.
For SUN engine testers WITH change-over switch for transistorized Coil Ignition Systems -
Red clip to ignition coil terminal 15
Black clip to ground
Bosch mini-tester EFA 226:
Red clip to ignition coil terminal 15
Black clip to ignition coil terminal 1.
I'm not going to pretend any of that made sense to me. I guess I'd try the first connections above if using a dwell meter for non-transistorized igntion systems and see if the reading looks halfway right. Otherwise, it looks like a dwell meter that specifically works with transistorized ignitions might be the way to go.
One last thought is that point gap and dwell are directly related. An accurately set gap should give dwell within specs (assuming the distributor shaft bearings are in good shape). Good luck!
George Davis
'69 280 SL Euro manual
