Replaced HEI module now won't start

[tx1572]

I swapped over to the VR circuit this weekend and I think I may have the base ignition settings wrong. It will start and idle but it misfires badly if I try to go over 2500 RPM. I switched back to the opto circuit and it runs well except for an occasional misfire when it's cold which, is why I wanted to try the VR. I thought I set it up according to the description in the manual but I could have missed something, this is the MSQ I was running while the VR circuit was being used. Also, the only way I could get it to fire on the VR was to turn R56 clockwise around 5 turns. I'd appreciate any suggestions

[trakkies]

The VR input won't make any difference to the timing, as such. But It does offer standard and inverted outputs. I'd try the inverted one - that may match what you were getting from the opto, and is easy to try.

It's normal to have to adjust R56 according to the actual input signal. Best way is to look at VR out with a scope and set for the best waveform. If no scope, turn it back a half turn at a time till the tach signal disappears. Then turn 1 1/2 turns clockwise.

[tx1572]

Thanks for the quick reply, I'll have to give that a try this weekend. I just bought my first scope so I'm still trying to learn how to set/read it correctly but it did look like it was triggering off the wrong side of the signal coming from the module.Would I leave the settings in TS the same as the opto if I use the inverted VR output?

[trakkies]

If everything like timing etc was ok with the opto input and all you had was a slight miss, I'd try and set the VR input to give the same (but 'better') signal. But I'd also check the timing using a timing light on the engine timing marks. If it doesn't have any, you'd need to create them.