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MG MGB Technical - 45DM dizzy & pertronix ignition


I have a 1979 MGB and I've recently attempted to install a pertronix ignition with my lucas 45DM distributor. The instructions provided with the kit are vague and unclear. I THINK I've installed it correctly, however the engine won't start after static timing. Any suggestions?

Ryan
M. Hutter

Do you have a spark at the plugs?
Fred H


Yes. Here's what I've learned so far. The pertronix ignitor ignition kit will not work with a ballast resistor. I statically timed it as best I could and I'm able to start the car now (with very poor timing). Now I can proceed to correct the timing.



Ryan H

I have Pertronix ignition in my 1976 MGB, and yes, it does work. I found that there are two units available. One of them is to be used with the ballast resistor and the other one is for the non ballast resistor cars.
Jim Webb

The Pertronix module requires that the breaker plate on which it is mounted be grounded for proper operation.

Typically a Petronix replaces mechanical points. The breaker plate in a points type distributor has a flexable braided ground strap connected to it to keep the plate at ground potential.

The 45DM distributor originally came with an electronic hall effect module mounted on its breaker plate. Since this distributor never had mechanical points, its breaker plate never needed to be grounded so it is missing this ground strap.

To fix, get a short length of flexible braid and connect one end to the breaker plate, the other end to the fixed base of the distributor. Allow enough slack in the braided wire to allow the vacuum advance to completely rotate the breaker plate.
Steven Rechter

One thing more to consider. I found this with mine. I had to advance my timing quite a bit from where it was. It has since been in for about 1.5 yrs and not been touched (knock on wood).
kids1

Why replace the 45DM electronic unit with a Pertronix? It is reliable and the CEI module is still available. A non-ballast type could be used in a ballasted car but has to have a 12v supply from the white or white/brown at the fusebox instead of picking it up from the coil +ve. But the Pertronix site lists MGB applications for 1975 on and not before i.e. ballasted systems only, however it has units for the 1950s TF and Magnette, which must be non-ballasted. Not only that it states the MGB replacement is for Lucas electronic ignition, so if the kit *doesn't* include the braided wire Steven refers to that is really poor. If the timing is way off with the Pertronix it implies the trigger point has moved, twisting the distributor will correct the timing, but there will be a different relationship between the rotor and the contacts in the cap and this could cause misfiring problems at one extremity of centrifugal advance or the other. Beats me why anyone bothers.
Paul Hunt

I agree with Paul.

The CEI ignition system is far superior to the Pertronix. The CEI is actually a repackaged, very reliable, General Motors HEI ignition system.

Steven Rechter

Steven to use the word reliable to describe the general motors HEI system makes me wonder if you ever did any work on GM cars of the 70s and 80s HEI has to be the worst system ever.The control unit died so often they were avail able at the 7/11 RIC
R E L Lloyd

This thread was discussed between 01/09/2003 and 05/09/2003

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