Hi Jeff,
Since Mallory is no longer involved (over 2 years now) we prefer to call them: Super-Mag or Sprintmag
I know, old habits die hard...I can't expect the earth to rotate the other direction at my whim in just 2 years. But I try anyway 'cause I'm stubborn.
The Super-Mag+ has a different stator winding inside...different gauge and number of turns so that our biggest magnet makes 9.9 - 10.3 amps at 2500 engine RPM. The 10 amp mag also requires the severe-duty points. And those require a bunch of other related hardware to make them fit. The 5 amp SM IV, 8 amp SM V and 10 amp SM+ all have the same magnet assembly...just the winding inside changes. So, find a healthy SM IV and get an upgrade to the V (winding swap) or the more expensive SM+ (winding and points upgrade). The biggest diff regardless of which one you run is to run the BIG coil.
Through experimentation on my car and through customer experiences, I've found with nitro, you just can't have enough spark at idle. The fuel it's burning at an idle makes a significant difference in how it leaves the starting line. After the throttle is wide open, I can't honestly say I can see a difference, but I've been changing main fuel delivery along the way too. I was putting 6 GPM to it, then 8 and now I'm over 11 GPM. Not sure it would still burn all that with the Super-Mag IV. I doubt it.
I ran a 5 amp Super-Mag IV and red topped coil for years and it did fine...no trouble. I put an 8 amp SM V on it with the small black coil and had to richen the idle. What really opened my eyes was just swapping the small black topped 28990 coil for a big 28901 monster coil. It totally dried things up to the point where I couldn't get it rich enough to wet the pipes and it would fall on it's nose. I upped the idle fuel pressure and idle nozzle sizes and could finally get it wet enough. Just from a coil change!
While experimenting with Super-Mag+ windings, we took one a little too far...it makes 11.6 amps at an idle. None of us figured it would live long with points in it...even the really good ones, but running it on my car was a great way to see what it would do without pissing anyone off. With spare mag at the ready, I've got 15 laps on it and the points look like new. Had to richen it up even more and it's a different beast off the line now for sure. It consumes a BUNCH of fuel at idle and pretty much demanded a hi/lo type idle circuit.
Next experiment is to swap out the 28901 coil for the 28920...it's the same size and shape but a different turns ratio. It makes huge voltage and spark duration...so much spark duration that there's almost no OFF time. The cutaway cap is a solid ring of fire above 8000 RPM. I won't sell one to a blower guy spinning high RPM because I'm afraid it would be a bomb. But a naturally aspirated motor and/or one that doesn't spin that high and it may be a great thing. Mine never sees more than 7200, so I'm going to make sure my rotor tang is firmly attached and give one a try this year!
