Thanks feral for the info as I always wondered what the use or uselessness was of these things for road users.

Good for a speedway car running high RPM but has no mechanical advance to make it suitable for road use. These Hunt maggy's give the same plug voltages as the S2 bluey conversion but only at very high RPM.

They also make engines hard to start if high comp is used and cranking speeds are low.
With magneto's spark strength varies proportionaly with rotational velocity of the magnet past the field coil, so very good at high engine speeds.

Still a good curiosity item though.

http://www.speedway.net.au/classifieds/adDetail.asp?cat_id=23&sub_id=50&ad_id=1273

Is this a good deal? well if so I hope its worth it to someone.