I'll Be Fine Tuning a factory '72 Thermoquad (6139S)
Update: Going back to the colder plug recommended in the factory service manual for 340. I have two sets of Champion RN9YC which have only a couple of hours on 'em (I believe made in Mexico). Cleaned up one set of eight with various sessions of brake cleaner, carb cleaner, and compressed air: see photos #1 and #2. (I will also replace the gaskets). Current plugs are Autolite AP 65 with a couple of hours on 'em that I will replace: see photo #3.
Note: Evidently the Champion plugs became all sooty when the coil failed. We will now see how they look after some run time with new coil/electronic ignition/wires.
Update: Going back to the colder plug recommended in the factory service manual for 340. I have two sets of Champion RN9YC which have only a couple of hours on 'em (I believe made in Mexico). Cleaned up one set of eight with various sessions of brake cleaner, carb cleaner, and compressed air: see photos #1 and #2. (I will also replace the gaskets). Current plugs are Autolite AP 65 with a couple of hours on 'em that I will replace: see photo #3.
Note: Evidently the Champion plugs became all sooty when the coil failed. We will now see how they look after some run time with new coil/electronic ignition/wires.