Wasted spark and negative polarity

[Lesliehedley]

I am running wasted spark coil packs on my 400SE which I've just finished installing. The engine runs ok and idles nicely. I believe that the odd cylinders are on the negative polarity side of each coil pack and the even cylinders are on the positive side. If I put a timing light on the even cylinders I get a good spark at a fast rate with the arrow on the induction pickup pointing at the plug. If I reverse the pickup, the light doesn't fire, which is what I would expect.

But, if I put the timing light on any of the odd cylinders, I get the light flashing at what looks like half the speed of the even cylinders and I get the same if I reverse the pickup direction. I would have expected the pickup to only work in the reverse direction because of the reverse polarity on that plug and at the same rate as the even cylinders. Can anyone tell me if this is normal or have I got something wrong?

[adam quantrill]

It might be a function of the pickup (is it the magnetic clamp type?)

If it's not "missing" and the hydrocarbon readings are good then it will be getting spark at the correct times (and not missing half).
Maybe borrow another timing light and put both on the same lead?