Triumph Repair: Coil overheating, ballast resistor, starter solenoid

Question
1971 spitfire mk4 (barn find, was parked since 1984)

Thank you so much for your previous answer about the stromberg carb. although after adjusting it I took it to the emmissions shop and it failed again... this time because the coil started burning (left a nice smoldering pile of hot oil on my engine shelf.) I'm beginning to think my little spit has stage fright.

I purchased a new coil that is internally resisted. (previous coil was not) and the new coil gets real hot and my spit starts sputtering after driving for a while...

The first coil was replacing the original coil and ballast 6v (I believe)

so my question is:

In order to run a 12v internally resisted coil does anything else need to be changed other than removing the stock ballast resistor?

IE: does it need different points? should the wiring be run differently? Scrap the points and get a pertronix?

Answer
Hi Nate,
The 71 Mk IV Spitfire is suppose to have a 6v coil and a Ballast resistor and a bypass wire from the starter solenoid to apply straight 12v to the 6v coil ONLY during cranking. When the key is released back to ignition the power to the coil goes through a ballast resistor.

Two things you need to do. One is to check with your wiring diagram to confirm that your car is wired as it should be and second is to put a volt meter across the battery and read battery voltage (12.5v or so) then start the engine and set the RPM at about 2000 RPM and read the volt meter again. It should read 13.8 to 14.5v but not more.
A 12v internal resisted coil can be used but not with a ballast resistor. Some car owners do that.
Howard