Pertronix 40kV Flamethrower Ignition Coil, Chrome, 3 Ohm, Oil Filled fits in the stock distributor clamp, and is compatible with points or all poins replacement devices, with it s 3 Ohm Impedance. Proper coil impedance ensures no burned points or modules! While it s the perfect coil to go with the PerTronix Ignitor breakerless ignition, the addition of this 40,000 volt Flame-Thrower canister coil can benefit virtually any distributor type inductive ignition system.;Its higher voltage allows larger spark plug gaps or firing through plug fouling.;This coil is internally resisted just like the stock blue coil so it is compatible with everything. You can use this with CDI ignition systems, though those systems run best with 0 Ohm Resisted Coils.;This coil is oil filled, which provides great heat control. High vibration applications (Off Road) should use our Epoxy Filled version of this coil.;A 3 Ohm Coil Impedence is compatible with points, and points replacement devices, in 12V electrical systems. We recommend you check your existing coil, so first make sure you have 12V going to the terminal 15 on the coil (Terminal 15 is positive, terminal 1 is negative (think of 1 sideways being negative). If you do, then pull the wire out of the center of the distributor with a rubber handled pair of pliers, and hold it about 1/4 from the metal clips that holds the distributor cap on. Have someone crank over the engine, and there should be a nice blue spark that goes from the end of the wire you pulled out of the center of the cap to the metal clip. It should look and sound strong, and should be easy to see, even in daylight. If it looks thin and weak (yellow is weak, blue is strong), then the coil windings may be giving out.;Another test for your coil is to use an Ohmmeter and with all the wires taken off the terminals of the coil attach the positive and negative, red and black, wires of the meter to first the small terminals (Positive and Negative) that are printed or stamped on the coil. You should have a reading of at least 3-4.5 ohms, which is the resistance reading inside the coil. A bad coil will show a higher reading than 3-4.5, you want less resistance.;Next, place the red or black lead from the meter to the center of the coil (secondary post), and to either one of the terminals, again 1 or 15 on the coil. You want 9500-10000 Ohms, sometimes you ll see less, but you don t want to see something like 11,000. Or if you have no reading in either case, the coil is trash and in need of replacement.