[James]

I don't believe buying a cap will fix the problem. The stator that is below the rotor is made for an odd fire engine (the moving targets are not evenly spaced). That's is why when installing an odd fire distributor that the number one on the distributor aligns with cylinder 1 TDC on the compression stroke. Otherwise (getting it off by one post on the distributor by moving the wires trying to make it aligns) the timing will be further off on all cylinders. Odd fire timing intervals is: 90°-150°-90°-150°-90°-150°. Even fire timing intervals is 120° between cylinders.

I hope this help. And yes, you will need to buy an even fire distributor to make it work correctly.