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MG MGB Technical - Dizzt Wobble

At the rotor, what slop is ok on the shaft: none or some?
vem myers

Hi Vem, If you are still running points I would suggest zero tolerance for radial slop, end float is unlikely to cause problems, however if you are running electronic trigger "hall effect" a small amount of play will probably be O.K. . The lumenition optical type will tolerate radial play with little effect but excessive end float can cause the chopper to rub on the optics which can eventually go blind Jim
jim soutar

In a perfect world, none. You should see a very small amount of movement on a distributor shaft, especially when running with points. Chevy 6s were notorious for this, in the '60s and '70s, and I had to set the point gap to less than .0030" just to get them to run. When hooked up to the osiciliscope, the dwell would be all over the place. Eventually, the rotor will start to hit the cap's terminals. It might be time to send it off to Jeff S. for a rebuild and re-curve. RAY
rjm RAY

The rotor should be a firm fit on the shaft in my experience, i.e. none, and not just in a perfect world. If yours is loose there is definitely something wrong that needs fixing. You will get rotational movement between the upper and lower halves of the shaft which is the way centrifugal advance is applied, and maybe sideways play in old units which is bearing wear.
PaulH Solihull

Jim- Soas to bend it like Becham, Have you done better than the 124HP at the SC rear wheels? Vic
vem myers

Hi VEM. Spent some time improving the advance curve which has helped to give a wider spread of power throughout the rev range. Engine has now covered approx 4000 miles and revs more freely. Unfortunately time constraints have prevented me from taking it back to Peter for another dyno run. Perhaps this year I might be able to have another test. Nice to hear from you again. All the best Jim
jim soutar

Vem, I'm using a Moss blower on my '67, with an overbore of .040", a ported and polished head and a Kent 285 cam. I tried using the distributor that Moss recommended, but it was such a piece of junk that I just set it aside. I tried my tried and true Mallory dual point, but it wasn't up to the task either. I finally went with a GM based HEI unit that Davis Unified Ignition Systems put together from a '80 4 cylinder Jeep application. They make their own coils and modules. The coil puts out 50,000 volts and they recommend that you open your spark plug gap to .055". To control detonation, while under boost, I use an MSD Boost Timing Control Master that allows me to control spark retard from 1 to 3 degrees, per pound of boost, from inside the car with the turn of a knob. This has produced an engine that delivers an amazing amount of low end torque as well as upper end horse power. I haven't been able to get it dynoed yet, but I'm sure that the numbers will be impressive. Setting up a good ignition system was the hardest part of the supercharger installation. This is where Moss should invest some further research and development IMHO. RAY
rjm RAY

Cripes! Thanks Ray for some more info on supercharging, this is now duly logged in my little book under ignition. thanks Mike
J.M. Doust

It's a great system and delivers quite a lot of juice to the plugs. The only drawback is that the distributor is huge since it has the coil built into the cap. However, due to its size, if the heater valve starts to leak, the coolant will never reach the distributor cap. It took a while to get everything to work together, but it has been more than worth the effort. RAY
rjm RAY

This thread was discussed between 11/01/2011 and 19/01/2011

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