Question about wiring coming through bulkhead firewall, including the resistance wire

Hi folks,

I’m in the process of replacing the wires that come through the bulkhead firewall into the engine bay, including removing the resistance wire (hiding it actually as per the help instructions).

I have a couple of questions but I will start with some info:

The following is the bulkhead firewall wiring based on Figure 12-108 in the Cadillac repair manual:

To starter:

18 G Yellow (goes from starter to coil directly)

12 G Dark Blue

10 G Red

To coil:

20 G White with orange and violet cross tracer

18 G Yellow (goes from starter to coil directly)

To thermostat:

18 G Dark Green

Here is what comes out of my bulkhead firewall:

12 G Dark Blue that goes to a connector. The connector also has the 18 G yellow coming in AND out of it. See photos below.

10 G Red

18 G Dark green

On my setup, the white resistance wire is connected to a 18 G Yellow wire via a clip that connects to the coil (see first photo). If I delete or disconnect the resistance wire, I assume I need to run a new 18 G yellow wire from the coil to the starter, correct?  

If yes, then I can delete the connector that splits the dark blue wire (first photo) and just run a new 12 G Dark Blue wire to the starter?

I also have a white wire in the bulkhead firewall harness that loops from one side of the loom to the other with a female connector on each end (see photo below). I don’t see this wire in the repair manual diagram, so I have no idea what it’s for. Any thoughts?

Thanks in advance for both your input and patience as I fumble my way though this.

Oh and here are a couple of progress photos for your entertainment!

Balanced crankshaft

My good friend Bruce checking tolerances.

Almost there...

New vacuum lines run, new brake hard lines, suspension work underway. Then everything else...

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That's his good friend Bruce not Chris Gill, Tony

Clovis is correct. That's Bruce. He's built over 2,000 engines during his career including numerous race engines. Bruce is a perfectionist (think OCD for machinists) and helped me build two other high performance engines previously.

look to see where your  R is located . is it just after P or park ? or is it all the way down to the bottom   

R is all the way to the right (bottom).

you have a hydramatic not a tubo . 

you are doing a great job . thanks for posting as we all learn a little

Awesome. Thanks Mike.

I'm removing the white wire then, unless there's some other reason to leave it.

It's interesting/eye opening to be a newbie again in terms of vehicle knowledge on this build. With MGs, and especially MG engine swaps, I'm usually the one giving advice!

Chris 

Giving you compliments you don’t deserve but that Bruce looks very professional and has soom good credentials to back him up I see 

Clovis 

thanks fot the heads up 

Enjoy 

If it’s a  stock 390 63 it can only have a Hydromatiic 

The THM is new to 64 — first year it came out 

need to always consider some kind of prior engine or trans swap —may have happened in the past to keep these cars rolling down the road 

Enjoy 

I still need some feedback on what to do with the yellow wire:

On my setup, the white resistance wire is connected to a 18 G Yellow wire via a clip that connects to the coil (see first photo). If I delete or disconnect the resistance wire, I assume I need to run a new 18 G yellow wire from the coil to the starter, correct?

If yes, then I can delete the connector that splits the dark blue wire (first photo) and just run a new 12 G Dark Blue wire to the starter?

With factory wiring you have a yellow wire from starter to the + side of the ignition coil. This provides a full 12 volts at start up. This wire should not be removed.  It can be any color wire you wish to splice in there but might as well make it yellow to be consistent with the shop manual.

The resistor wire kicks in when the ignition switch is turned back to run. This resistor wire attaches to the pink ignition wires behind the firewall. This wire should not be removed or bypassed if you are still running points. If you are running Pertronics Ignition or other setup without points you can bypass it.   If you bypass the resistor wire with a regular wire to deliver a full 12 volts to a setup with points, the points will burn up and fail quicker.

In reading the original post on page 1 I am not seeing any mention about points being bypassed. Perhaps it is on one of the nested replies.   So my question to you is why are you asking about removing the resistance wire?

I am going to install an electronic ignition system, specifically an HEI conversion:

https://www.davessmallbodyheis.com/services/basic-pricing-information

Based on the help article, I can hide/remove the resistance wire because it isn't needed, unless I'm missing something?

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