Distributor Rotors, Lucas black and Premium Red buttons.

When running a converted Lucas distributor using the Patton Machine distributor upgrade we suggest that the black Lucas rotor button be replaced by a more modern premium red button capable of handling the hotter spark of today’s technology. The hotter spark is (+40KV) due to bypassing the original resistor wire found on many British cars. The original coils are designed for a ballast resistor are actually 8 or 9V coils but when running a bypassed ballast they receive full ignition voltage of 13.1 to near 15V thus outputting a significantly stronger spark. The original coils can easily handle the hotter spark in a TBI system because the GM ignition module is current limiting. Will it run with a black rotor, sure, but you may experience a sudden unexpected loss of spark especially in cold weather or during a long run. When the rotors fail they short out internally to the distributor shaft with no visible evidence of the failure. This has been not just a failure with bypassed Lucas ignitions and has been a common failure with many unaltered Lucas distributors for numerous years. Even more common if the original coil has been replaced by a hotter aftermarket coil. I am reluctant to upgrading to a “super coil” as the diameter of most Lucas distributors is small so there is a strong possibility of the spark cross talking or jumping to an adjacent cylinder.  

Failure symptoms: you have a black rotor button, sudden shut down of the engine as if the key was turned off.

Testing: The coil will be sending a high voltage spark to the distributor cap but nothing gets to the spark to plugs. Easily confirmed with a timing light, flashes when connected to the coil wire; nothing when connected to any plug wire. My suggestion is to purchase two red rotor buttons, one for the distributor and another for the glove box so that one day you may be able to aid another British car found dead alongside the road. Most all of the big British parts houses carry the premium red buttons, including Moss Motors, see  PDF below for more and part numbers.

From Moss Motors an excellent PDF with more info:     https://mossmotors.com/media/instructions/151-805_151-865_872-785_INST_WEB.pdf