I ran across this article in Hemming today. I thought worth posting here.
Thks for that I didn’t know that different manufacturers can have heat ranges in opposite directions
heat range numbers do vary by manufacturer…not only in direction–hotter colder, but also in the heat range of a given number–some have a wide range, some quite narrow. A few key things…correct gap and heat range: do not overtighten–if threads are clean so you can hand spin to firmly in–then it is just 3/4 of a turn more if new crush gasket…and just 1/4 of a turn if a used plug/gasket. Many plugs now are high resistance plugs…5,000 ohms or more, often an “R” in the number, and most new plug wires are very high resistance 10,000 to 40,000 ohms per foot. We do not want that resistance in the XK ignition system. You can get away with R plugs…but the wires–no. Use low resistance plug wires. The ignition system all works together…so a good coil (Lucas Sports is 40,000), good points, condenser, rotor, cap, correct gap,–wires and plugs. Then timing.
The XK engine runs fine on the copper electrode plugs. Platinum is no advantage and Iridium is not optimal for the XK engine.
Most are happy with NGK BP5ES…which is a little hotter plug than the sometimes used BP6ES…colder for more sustained higher rpm use. You can cross ref those to other brands. NGK has a little wider heat range than some others–so just those two plugs cover the useable street driving range. With modern fuels, a sound distributor / coil and wires etc…the gaps can be revised form old factory spec–to a little wider gap. On the 120, 8-1 ; I use .028, points at 016, timing 8-10 D BTDC.
Nick, one may wish to keep in mind when talking about an “XK” ignition system, many people have altered their ignition systems to Pertronix, 123, various non stock coils, etc. Many of these various ignition systems often have different requirements, some requiring higher resistance in the plug wires than a stock system.
When one chooses to modify with modern parts—- they can get assistance from others
Nick, not quite sure what you are saying. Posters are constantly coming here for help with all sorts of modern modifications and there are usually many willing to help. I do not know of anyone expecting them to go to a different forum.
Oh ! I was just saying that I don’t know much about non original parts so I can’t offer technical support for them. By “others” I mean others here who may know about , say, a 123 distributor or a power steering conversion.