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MG MGB Technical - converting to electronic ignition

I installed a pertronix in 1980 mgb with 45D distributor. Points and condensor were connected to a small black box that was not wired into the coil. Car wont start connected to the box but runs with pertronix hooked direct to coil. I cannot find reference to the box in my Haynes Manual or anywhere in the archives. When I started the car it idled at 2,000 before the install it idled nicely just below 1,000. I found my strobe light is broken and I have adjusted timing as best I can until I can purchase a new one on Saturday. Car drives well, but I cannot seem to get the idle to maintain below 1,000. When I turn on the headlights, the idle dips so low the car wants to stall. Is this because I cannot get the timing correct without a timing light? Distributor is in good shape, car has 93,000k and typicaly runs very well.

I have a 25D, but I found Pentronix has different wiring sckemes. They helped me
Frank Baker

If you have a North American 1980 it had electronic ignition from the factory, one of two types. If it has points, and they are connected to a black box, then it is an after-market PO mod. A Pertronix *should* be connected directly to the coil, but make sure the distributor has a ground wire conencted between the moving points plate and the body of the distributor. If it has points it should have anyway, but check to be sure. A 1980 would originally have had a 6v coil and external ballast resistance, which can affect how the Pertronix is wired, but again this could have been replaced with a 12v coil and no ballast, or even worse a 12v coil *with* the ballast still remaining.

A timing light is certainly the preferable way to set the timing, although in a pinch you could use static timing, 7 degrees seems the norm where it is given for late-model cars. Slowing down that much with just the headlights points to a very poor state of tune - or very powerful headlights!
Paul Hunt 2

This thread was discussed between 28/06/2007 and 29/06/2007

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