Return to General Engine Questions

Initially it is most likely that the coil simply needs replacing due to old age. However if the problem keeps re-occurring there are several factors to examine.

Firstly note that the Pre-Crossflow engine is usually positive earth. The old coils were marked CB (Contact breaker) and SW (Switch) the new coils are marked + and - based on negative earth cars. In this situation remember to reverse the polarity. i.e. + goes to the Contact Breaker and - goes to the switch.

If the problem continues consider the use of a ballast resisted coil, together with ballast. This enables the circuit to run at 9V instead of 12V and therefore it runs cooler. A ballast coil and relevant ballast are required for this, together with a heat sink for behind the ballast. A simple job, parts are available from the Freeman Shop.

A more complicated method of cooling the coil and often used on very classic engines (pre Freeman) is to make a water jacket by coiling copper tube around the coil, feeding from the engine cold water intake (after the pump). - a last resort?

However before resorting to more elaborate fixes there is probably a hidden reason as to why the coil continues to overheat. This may not be obvious at first sight. Look at the colour of the points, are they blackened? Ensure that the gap is correct as this alone can cause over heating.

If they are blackened it probably means the initial cause of the problem stems from below the distributor, i.e. tappet clearance, timing or excessive movement on the timing chain.

If they are not blackened look at the low tension cables and connections. Frayed connections on the coil, switch, supply cable to the switch will cause resistance (the equivalent of a blocked pipe). This resistance will not allow the coil to run efficiently and it will overheat.

In particular check the HT lead and it's connections between the coil and distributor cap.