Ignition coil
Rolls Royce and Bentley: Cars fitted with 6 cylinder engines: Rolls Royce Silver Dawn and Silver Wraith plus Bentley MkVI and R Type (1946-55) • Rolls Royce Silver Cloud I plus Bentley S1 (1955-59)
with screw-in HT lead terminal and approx. 2.8 Ohm primary resistance. Non ballasted type
Ignition coils have a “+” (POS) and a “-” (NEG) next to each of it’s two low voltage terminals. That’s because coils need to have the same polarity as your system: wiring backwards will weaken the spark. The wire that goes between the distributor points and the low voltage terminal on your coil, the low tension lead, should be connected to the terminal that is labelled for the same polarity as your battery ground. For instance in an early positive earth British Classic Car, the low tension lead should attach at the terminal marked “+” (POS). If that same vehicle were converted to negative earth the coil should be turned 180 degrees in the holder and the wire connected to the “-” (NEG) terminal.