Delco distributor caps don't all interchange

Posted by Jack Vines On 2013/1/9 13:11:57

Recently I was asked to consult on two different distributor problems caused by the same mistake.

The later GM Delco distributor cap can be made to sit on the Packard Delco distributor, but it won't function correctly.

In the first instance, first the rotor hit the inside of the distributor and broke. The replacement rotor then broke the cap.

This happens because the later GM distributor cap is .100" larger inside the mounting area. This allows for enough misalignment for the rotor to hit.

In the second, the car was running roughly and misfiring. The late GM cap isn't properly indexed to the Packard distributor cam and when the points opened, the rotor was between poles in the cap. The spark could go either way.

Bottom line - make sure to buy the correct cap. It should fit tightly with absolutely no play on the body of the distributor.

jack vines