Allison/Crane XR700 optical ignition install issues

[kmead]

On Saturday May 21 we had a WMF Garage day. One of the tasks was to install a XR700 system to replace the points in a 1978 dual point distributor.

The install was easy and with a bit of fiddling the car started with a lumpy idle. With a bit more fiddling it ran fine at idle. The shading/shutter wheel's center hole was slightly off center but it didn't affect the motion as the springs underneath located it properly and the wheel didn't wobble unduly as it rotated with the shaft.

The problem started when we tried revving the engine. It would start missing almost immediately and we could see the spark being "dropped" with the timing light in addition to the engine failing to rev.

To trouble shoot we tried a few different ways of delivering 12v to the coil using an external battery unfortunately to no avail. We ensured we had isolated the system from the point changeover relay and so on. We double and triple checked the connections and found nothing incorrect. We tried it without the tachometer wire attached. We tried it with two different coils.

We then reinstalled the dual points and the engine ran perfectly.

Any suggestions or pearls of wisdom? I would like to try again but have some ideas for more trouble shooting before doing so. Thanks!

[majicwrench]

It's just me I know, but if car runs perfectly with dual points, why.........

[kmead]

It is a case of the owner wanting to do an upgrade for perceived future reliability. It does work fine as is and we were leaving the existing system in place so he could easily go back if he needed to (in case of failure of some subcomponent).

Karl