LS1 re-wire/clean up
 

Hey guys, looking for some help here and some direction before I move forward, hoping this is an easy task and would love everyone’s input!

The way the previous owner just laid the harness against the firewall behind the motor and how he mounted the ECU always bothered me, just seemed as if there was zero thought gone into it, and it drives me crazy.

With that being said, I would really like to clean this up, and try to hide these wires a lot better to show off this sweet little swap it has.

Listed are some pictures of where I stand at the moment. The ECU is mounted pretty much right behind the motor under the dash, and the harness is then ran through the firewall pretty much behind the pedal. You can see where it comes out and immediately tucks behind the motor. Everything was just kinda stuffed back there, zip tied, and hung off the back side of the ECU bolts.

Question is, how would you attack this to clean it up? Frankly, I’m slightly intimidated, but ready to figure it out.

Thoughts?

Re: LS1 re-wire/clean up
 

On my 68 C10 with a LS swap I made a couple of brackets and mounted the GM ECM/fuse/relay block right behind the glove box. I had to section the glove box a bit to get every thing to fit.
I used a Painless 21 circuit kit to rewire the truck. I welded up the stock fuse block hole and made a new hole behind the left inner fender for the chassis wiring harness.
For the engine/trans wiring harness I made a hole in the firewall behind the engine just below the cab heater housing.
I love to hide wires.
Couple of pics.

Re: LS1 re-wire/clean up
 

I spent several long months on my wiring. I tried to make it as neat as possible along the way.
With an LS swap, you gotta have wires but they can be hidden and routed neatly. Black braided loom make it blend in.
LS1 from an '02 TransAm in my '67.
With VA AC and all the hoses, I just didn't have room to cram the ECM and the fuses behind the dash.
I mounted the PCM on the back of the core support down low and out of the way.
I built a load center for the fuses and relays and mounted it right above the PCM.
Re-routed all the headlight and turn signal wires as well as the engine wires that come out of the firewall bulkhead connector.
I do have some wires behind the engine but they are all out of sight.
Attachment 2444961

Attachment 2444962

Attachment 2444963

Re: LS1 re-wire/clean up
 

Both of those are VERY clean bays gentleman, very clean. I aspire to get mine looking half as good!

So far my plan of attack in my head has been something like this.. Mount the ECU to the back of the glove box (the glovebox is plastic though should I be concerned with heat?)

Re-route some of the engine connectors through a hole or two already in the firewall on the driver side, then maybe drill another on the passenger side to accomplish the same thing. Just enough to sneak a connector through and leave the bulk of all the actual wires and harness in the cab and work on tucking them up as best as possible behind the "dash"

Sounds better in my head.. I gotta get out there in the garage and stare at this thing little longer over weekend

Re: LS1 re-wire/clean up
 

I didn't mount the ECM to the glove box. I made a bracket that mounts to the heater housing.
Looking at your pics it looks like all the wires under the steering column are a bit of a mess. No disrespect intended but if you would have an issue and had to trouble shoot something it could be some work to work thru the bundle of wires shown in the under dash pics.
I can't tell you how many hours I've spent staring at my hot rod projects trying to figure out the best way forward. LOL.
Just for chuckles pics of a 67 Nova project I did a number of years ago. PO got totally hosed by a LS swap "expert".
Before and after pics.

Re: LS1 re-wire/clean up
 

Agreed!

It’s all a mess, but we’re going to try and correct it as best as possible before summer hits.

Re: LS1 re-wire/clean up
 

After spending a few hours disconnecting everything and brainstorming.. this is where I'm at.

21 painless circuit is going to stay where it is. I 3D printed a bulkhead cover that'll cover it up some and make it look a lot more slick. I also already cleaned a lot of the mess up under the dash once the engine harness came out so that helped a lot also. I think i will have to extend a handful of wires from the ECU to the relays for the fans and whatnot. They are already mounted perfectly loomed, organized and bolted to the core support and id rather not do all that again if i don't have to.

Here are my thoughts with the engine harness..

-Mount the ECU to the passenger side inner firewall on a bracket I made that will connect to the new bolts coming in from the AC delete panel. This will position the ECU into the top corner tucked up and away from everything.

-Mount the Fuse block to the back of a new style plastic glove box.

-Run the harness along the top/inside of the dash as best as possible to keep it out of sight. Drop it down somewhere dead center right above the transmission tunnel. Thinking drill a 2-2 1/2 inch hole where i can run all the connectors back out into the engine bay just above the carpet line.

I think realistically you'd only catch maybe a few inches of harness coming down the firewall and going into the new hole when sitting in the driver or passenger seat which I'm OK with. This is the easiest route that I've come up with so far, it sounds o k in my head at least.

What do you guys think?