HEI questions

Greg Woods gwoods at symtx.com
Tue Jun 10 14:45:49 GMT 1997


I have a question on the ~ 86 GM distributer / coil setup.
my question pertains to the dual plug coil models.  Their 
are 4 wires coming from this coil.  2 go to the wiring harness
(1 of which is ignition +12V, and the other which is tach), and
2 go to the distributer.  These distributer wires are the ones
I'm confused about.  Ones pink and ones black I believe and they
are of course trigger wires coming from the GM HEI module.  But
what does the signal look like on these lines?  I would expect 
one line to be 12V and then go low whenever the coil is supposed
to fire.  is this what happens?  howcome it takes 2 wires?

Also, the timing is controlled by the ECM.  The rotor looks to me 
like its permenantly attached to the spindle which is turned by 
the cam shaft, right?  How does the ECM change the timing if it can't 
alter the rotor position??  I'm kind of a newbie so if these questions 
are stupid please be gentle!:)

I am doing a GM FI swap to my JEEP which has a MSD ignition unit
and am trying to figure out how to wire all this together.

TIA

greg woods
gwoods at symtx.com
austin tx
86XJ





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