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Old 05-05-2017, 12:07 AM   #1
OregonNed
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Wiring question

I've been working on some under hood projects, which included some rewiring of cobbled up leads by the previous owner(s). First of all, the truck runs fine - but in looking at the positive coil lead, the wire from there that is tapped into the wire going to the solenoid, (not original wiring, by the way) - ends up bypassing the top firewall wiring plug, (its cut off flush) and instead goes into the firewall and is plugged into an ignition unfused spade. This doesn't appear correct by the wiring diagram I have at all. Can it be a problem waiting to happen?
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Old 05-05-2017, 01:10 AM   #2
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Re: Wiring question

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Originally Posted by OregonNed View Post
I've been working on some under hood projects, which included some rewiring of cobbled up leads by the previous owner(s). First of all, the truck runs fine - but in looking at the positive coil lead, the wire from there that is tapped into the wire going to the solenoid, (not original wiring, by the way) - ends up bypassing the top firewall wiring plug, (its cut off flush) and instead goes into the firewall and is plugged into an ignition unfused spade. This doesn't appear correct by the wiring diagram I have at all. Can it be a problem waiting to happen?
That wire is fed by an ignition on source, normally from the key switch. It should be a pink wire that runs from the key switch ignition terminal to the inside of the firewall block behind the fuse panel.

It sounds to me like someone might have installed an HEI distributor and was going to use that terminal and cut off the ignition resistance wire that goes there. In any case the wire that you have now if it was on the firewall block by the master cylinder has been rerouted to the fuse panel. The IGN Unfused terminal is a key on power source and should work just fine for the alternate coil ignition source.

You have to be sure it has the resistance wire incorporated or it will burn up your points and maybe the ignition coil. If it is not the resistance wire, you can install a ballast resistor 1.8 ohms, in series with the wire, and it will serve the same purpose.
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Old 05-05-2017, 10:29 AM   #3
OregonNed
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Re: Wiring question

Thank you for the insight. I will do just that. The resistance wire must be the alternating orange and purple wire in the diagram then?
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Old 05-06-2017, 12:07 AM   #4
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Re: Wiring question

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Thank you for the insight. I will do just that. The resistance wire must be the alternating orange and purple wire in the diagram then?
Yes it's illustrated in the diagram. The second wire in on the right side, it connects with the starter resistance bypass wire.


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Old 05-06-2017, 12:45 AM   #5
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Re: Wiring question

Perfect. I'm going to replace the wire I described that is bypassing the bulkhead and will be also adding the ballast resistor I ordered in series. You show the fusible link circled. I also recently installed a 16 gauge fusible link as shown and I was also missing.
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Old 05-06-2017, 11:48 AM   #6
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Re: Wiring question

Have you considered the HEI distributor? It is almost plug and play. You just drop it in on no. 1 cylinder compression stroke and run the wire from the fuse panel to the BAT terminal on the distributor and set the timing. No ballast resistor needed. Easier starts, smoother running, hotter spark.

While you're at it how about the internal regulated alternator conversion, Then there's the headlight relay mod. Oh and how about disk brakes? :LOL
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Old 05-06-2017, 07:10 PM   #7
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Re: Wiring question

I'm actually trying to figure out my distributor as I'm not very good at identifying them. I'll post some pictures here in a few for help
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Old 05-06-2017, 07:18 PM   #8
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Re: Wiring question

To me it looks HEI with an external coil
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Old 05-06-2017, 07:19 PM   #9
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Re: Wiring question

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Old 05-07-2017, 12:13 AM   #10
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Re: Wiring question

Well well well you have been hiding things from us. What you have is a pointless ignition module in the distributor. It is not the traditional HEI distributor but is like a mallory unit or a standard gm points distributor with a Pertronix ignition installed.

This brings up an interesting idea. Some of these pointless ignitions do not require a resistance wire or a ballast resistor, which might account for the clipping of the wire in your case, and running the power wire from the fuse panel IGN unfused terminal to the coil. There are several of the Pertronix coils which need to run on the full 12 volts from the ignition source and your Mega Fire coil may be one of them.

Here's a good picture of an HEI distributor. See how much bigger around the body is.


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Old 05-07-2017, 12:20 AM   #11
VetteVet
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Re: Wiring question

Well well well you have been hiding things from us. What you have is a pointless ignition module in the distributor. It is not the traditional HEI distributor but is like a mallory unit or a standard gm points distributor with a Pertronix ignition installed.

This brings up an interesting idea. Some of these pointless ignitions do not require a resistance wire or a ballast resistor, which might account for the clipping of the wire in your case, and running the power wire from the fuse panel IGN unfused terminal to the coil. There are several of the Pertronix coils which need to run on the full 12 volts from the ignition source and your Mega Fire coil may be one of them.

Here's a good picture of an HEI distributor. See how much bigger around the body is.


Attachment 1649580
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