Thanx JH i have the stock dizzy.Was going to do the cap and rotor and wire upgrade with the MSD module.Would the 7 pin module be just as good as the MSD.How would the 7 pin module wire.
Great thread Merry Xmas
This is kind of complicated,
But, you can use the GM 7 pin module directly with your computer to control timing,
Then add on the MSD CDI module, triggered by the 7 pin module/Computer to get CDI discharge at the plugs.
This saves buying a tach adapter also...
Since you are triggering the ignition through a factory module, the computer interfaces with the factory 7 pin module.
The output of the module that would normally connect to the coil actually wires to the MSD CDI unit, and triggers the CDI.
I know it's the equivalent of TWO ignition modules, but it keeps you emissions legal,
It lets the computer control the timing curve so it works better with the fuel injection,
And it still gives you 600% increase in spark energy.
MSD has diagrams on the web site for this install...
Same as adding an emissions legal CDI to a GM Factory fuel injected vehicle...
Just find the diagram for a 7 pin GM module and you are off to the races.
Neither module cares what distributor you have, the trigger output will work with the 4 pin module, the 7 pin module or the CDI module.
Your stock distributor will work with any of them trigger wise, but you may have to lock down the vacuum advance and centrifugal advance since the fuel injection computer will be controlling spark advance.
When I do this,
I either wire sold where the springs are so the centrifugal advance can NOT work,
or a run a screw through between shaft plate and advance head to lock down the centrifugal advance.
Your fuel injection will know vacuum signal through the MAP sensor, so vacuum advance isn't needed.
To stop the vacuum from working, you simply remove the vacuum line to the distributor and plug the vacuum port.
When some 'Inspector' sees the vacuum line is missing, I've had to improvise,
So I shove a 'BB' in the line and put it back on.
It's not working, but it's there for the 'Visual' inspection...
Sometimes it's just easier to go along with the game than try to explain to the idiots what is going on...