holley 4d_ efi changes??

[Raymond C Drouillard]

I know that the duraspark works because that is what is being used right
now.  I am using the stock duraspark system (mechanical and vacuum
advance) to trigger the Jacobs Omni Magnum box.  The original system is
also triggering the Holley Pro-Jection system.  In fact, I have to use a
secondary trigger because the Jacobs box won't reliablly trigger the
Holley ECU.

I have been running it that way for a year, even though the secondary
trigger is a jerry rig as far as I am concenned (it offends my
engineering sensibilities).

Anyhow, I took an old seven-wire GM HEI module (I got the diagram for it
off the diy_efi site) and mounted it to a piece of aluminum for a heat
sink.  The Holley will plug directly into that module, so I put the
original connecter on it and plugged it into the ECU.  I removed the
Holley's tachometer wire from the old duraspark system because the ECU
will now be triggered through the GM HEI module.  I hooked the output of
the module up to the Jacobs box.  When I hook the HEI relucter to the HEI
module and give it a spin, the Jacobs fires and the injecters fire.  This
indicates that everything is working.  When I hook the Duraspark relucter
to the HEI module, nothing happens.

The Duraspark is a standard relucter/coil type system.  There are
actually three wires coming from the distributer, but one is a ground.  I
suppose if I fiddled around with it enough, I could get it to work.  I
was hoping that someone would know what is happening and save myself some
perhaps unfruitful experimentation.

Ray Drouillard


>Is the Duraspark a reluctor/coil type distributor?.  Did you test for
>800-1000 ohms?  Is it any good?
>Try a 1K resistor, and LED across the two wires from the dura.  A
moderate
>spin by hand should make the light flicker.  Just for grins try
both"polarities"
>One is "hot", and the other grounded.
>  I've heard from another source where one duraspark worked, and another
>didn't.
>Bruce
>
>>
>><snip>
>>
>>>>One feature that I have yet to use is the programmable ignition 
>timing.
>>
>>>>Does anyone here know how to get a GM HEI to listen to a Motorcraft
>>>>Duraspark pickup?  If someone has a copy of the doctor's guide to
>>>>optomizing your ignition, I would appreciate a quick recap or scanned
>>>>page or whatever.
>>>
>>>If there are two wires leading from the pickup coil in the
distributorr
>>>and if thye have 800-1000 ohms resistance then just wire them into
>>>the gm module, as "normal" the thing is that the can be reversed so
>>>you need to make sure your set up is as advanced as possible.
>>>  I forget where but their was another posting just recently saying
>>>this was backwards (using the most advance combo, do to rotor
>>>phasing), might try it both ways, and report back (please)
>>>Cheers
>>>Bruce
>>
>>I tried that.  It wouldn't fire the module, no matter what polarity I
>>tried.  Someone with a 'scope looked at the output of a duraspark and a
>>GH HEI distributer and the duraspark had a stronger signal.  I
suspected
>>the module, so I hooked the HEI distributer to the module and twisted
it
>>by hand.  I was getting lots of spark and the injecters fired.
>>
>>The only thing I can figure is that there is an impedance difference or
>>one is grounded and the other one floats.  If I had a little equipment,
I
>>could make an adapter with an op-amp without any trouble at all.  As it
>>is, I don't know the characteristics of either signal.
>>
>>Ray

___________________________________________________________________
You don't need to buy Internet access to use free Internet e-mail.
Get completely free e-mail from Juno at http://www.juno.com/getjuno.html
or call Juno at (800) 654-JUNO [654-5866]