Help needed for wiring harness on LS3 swap

[MadMaxx]

So after almost selling the car 3 times in 10 years due to a divorce, money sucking lawyers and losing interest I think I may actually live to see it get done- 69 Camaro.

So I bought a LS3 525 hp crate motor almost a year ago from a GM dealership. It came with the ECM, wiring harness and gas pedal. I'm really close to needing the harness but am very concerned as to what the hell I need. I know they make harnesses for 69 Camaro's with LS motors. I was told the ECM, gas pedal and harness that came with the motor is Junk and I would need to get new ones per Spear-tech ( why?) I want this done right but just want to understand why and how without spending tons of extra money on stuff I don't need. The guy I spoke with seemed like he wasn't interested in my business or in helping. I don't understand how the LS3 communicates with my factory gauges inside the car. I have new factory tach, new factory gauges in my floor council. I'm running a tremic 5 speed. I have electric hide away headlight motors, after market A/C. I have no clue who to listen to or who will take the time to help. The car is brand new everywhere and has cost lots of extra $$$ because new stuff came out over the past 10 years and well you know how it goes.
Any help, suggestions are greatly appreciated.

THANKYOU.

[XLexusTech]

Highly recommend PSI save yourself a bunch of BS give them a call


http://www.psiconversion.com/

[QueenCitySpeed]

I can help. Shoot me a PM.

[MadMaxx]

pm sent...

thanks for all the replies and help.

[Vega$69]

If you bought a GM crate motor and it came with the matching GM Harness, ECU and Pedal it is NOT Junk.

Who the heck told you that?

PSI uses the OEM ECU and GM Pedal. Harness is a harness. I put a PSI in my LS7 T56 car. A GM performance set up in a LS3/480 swap in a 69 with factory gauges and the GM Perf set up in my new 69 build with an LS3/525 crate motor.

http://www.autometer.com/tach-adapter.html

http://www.autometer.com/ls-install-kit.html

If using the factory tach it is easy to make work. Speedo no problem. You will need the metric adapters for the OP and Temp sensors. If mechanical OP then install the metric to SAE adapter and run the line to the gauge.

Hit me up if you need FREE help Lol

John

[Trevor @ Tx Speed]

The GMPP harness and ECM aren't junk by any means, but the harness will require quite a bit of work to make it look good. GM builds the harness with a LOT of extra length on all of the sensors, so you'll spend days trimming it to look right. Both PSI and Speartech could set you up if you want to go with a custom harness. A custom harness would be something to consider if you're looking to run an electronically-controlled automatic trans. The GMPP kit isn't setup to control a transmission, so you'd have to buy an expensive stand-alone controller for it. That's where a custom harness and ECM can save you some money.

Trevor
Texas Speed & Performance

[Vega$69]

The GMPP harness and ECM aren't junk by any means, but the harness will require quite a bit of work to make it look good. GM builds the harness with a LOT of extra length on all of the sensors, so you'll spend days trimming it to look right. Both PSI and Speartech could set you up if you want to go with a custom harness. A custom harness would be something to consider if you're looking to run an electronically-controlled automatic trans. The GMPP kit isn't setup to control a transmission, so you'd have to buy an expensive stand-alone controller for it. That's where a custom harness and ECM can save you some money.

Trevor
Texas Speed & Performance

The OP has a 5 speed Tremec. No reason to spend a dime on a custom harness.

The long GMPP sensor wires can easily be shortened by pulling of the split wrap folding the wires to desired length and wrapping with nylon braid. You can do them all in an hour most.

Then it's just a matter of strategically placing the ECM and fuse box and tucking the excess cable into the pass side inner fender.

Can all be done in a day including beer breaks.

[Vince@Meanstreets]

BTW, where is the OP? wondering what direction he went.

[Ron in SoCal]

I have a brand new PSI LS3 / T56 magnum harness on the shelf if you need it.

[Trevor @ Tx Speed]

I agree that it will work. But, the number one complaint we get from customers with the GMPP harness is the extra length that requires trimming to make it look good. Most of our customers don't want to trim their new harness and/or don't trust themselves to do it. We had a customer order a custom harness last week that returned his GMPP harness. To each his own.

The OP has a 5 speed Tremec. No reason to spend a dime on a custom harness.

The long GMPP sensor wires can easily be shortened by pulling of the split wrap folding the wires to desired length and wrapping with nylon braid. You can do them all in an hour most.

Then it's just a matter of strategically placing the ECM and fuse box and tucking the excess cable into the pass side inner fender.

Can all be done in a day including beer breaks.

[Vince@Meanstreets]

I have a brand new PSI LS3 / T56 magnum harness on the shelf if you need it.

I didn't see that on your web site Ron? :computer:

Whats my dealer price?

[Vega$69]

You don't need to shorten, cut or re pin to do the job.

This is my new build in progress. The fuse box is mounted behind the pass headlight and all wire bundles are securely tucked in the inner fender along with the AC and heater hoses.

The sensor wires will be folded into power braid to the proper length

http://i103.photobucket.com/albums/m158/Johnthaxton/1969%20Blue%20Protour%20Project/IMG_0061%20800x600_zpso8cbe6uj.jpg

[droptop 63]

You don't need to shorten, cut or re pin to do the job.

This is my new build in progress. The fuse box is mounted behind the pass headlight and all wire bundles are securely tucked in the inner fender along with the AC and heater hoses.

The sensor wires will be folded into power braid to the proper length

http://i103.photobucket.com/albums/m158/Johnthaxton/1969%20Blue%20Protour%20Project/IMG_0061%20800x600_zpso8cbe6uj.jpg

Beautiful detail. My problem is space under the dash on a 63 nova once you try to make the Vintage Air box fit in the same space on the firewall. Any suggestions??

[ADiCarlo]

I vote for PSI I know and have seen a ton of people running their stuff.


Sent from my iPhone using Tapatalk

[alongfortheride]

I have not ran psi. I have now ran 2 Speartech units. 1 ls1 t56 and 1 lsa856. I must say the Speartech stuff is very nice. He will make it what ever length you would like. John is great.

[cpd004]

I've had both PSi and Speartech...the Speartech is the nicer looking of the 2 and seems to be better built. I could be wrong, though. It's cost is much higher. The braiding they use is the softer material making to easier to tuck in and around things compared to the corrugated stuff. There wires seem to be more pliable. Also, Speartech provides provisions for AC and cruise control. Their fuse panel is less bulky and no need to run wires down to the starter like with PSi.

Both companies are always quick to provide tech support.

I have no experience with a GM harness, but if I already had one....I'd definitely use it and spend money somewhere else. Something always comes up that you didn't expect.


BTW Vegas...that engine bay looks great!

[randy]

You don't need to shorten, cut or re pin to do the job.

This is my new build in progress. The fuse box is mounted behind the pass headlight and all wire bundles are securely tucked in the inner fender along with the AC and heater hoses.

The sensor wires will be folded into power braid to the proper length

http://i103.photobucket.com/albums/m158/Johnthaxton/1969%20Blue%20Protour%20Project/IMG_0061%20800x600_zpso8cbe6uj.jpg

my harness is complete and i second this. Hardest part is finding room to mount the fuse box and ecm

[Revved]

Getting ready to start my first LS376/4L65E / Detroit Speed Swap into an 80 Trans am... I've got the whole GMPP Package and I'm looking at those miles of wires and getting my solder and shrink wrap ready!!

[Vega$69]

Getting ready to start my first LS376/4L65E / Detroit Speed Swap into an 80 Trans am... I've got the whole GMPP Package and I'm looking at those miles of wires and getting my solder and shrink wrap ready!!

No reason to solder anything unless you are extending the wire lengths

[randy]

yes i didn't solder anything either. Everything on the gmpp unit is plug and play. i had to change the vss connector for the t56 magnum but that was it. Now the american autowire kit is a diff story. I didn't solder anything there either though

there will be a lot of wires that you will not use if you are using the gmpp kit. I made this and helped a lot
http://i30.photobucket.com/albums/c302/icemanrld19/Scan.jpeg (http://s30.photobucket.com/user/icemanrld19/media/Scan.jpeg.html)

[HPIcustoms]

I will echo the others, there is nothing wrong with the GM Connect-and-cruise style harness (GMPP controller) if you dont want to make any changes etc to the motor! Its good value, and for those who think it can't look sexy, I have products available to make the install clean! We are in the process of releasing mounting kits for model specific LS3 installations, with hidden ecus and harness cleanup. For the universal stuff, we now have a braided wrap kit to clean up the factory supplied harness, comes with tools for install, cloth 3M tape, and mounting hardware and enough sleeve for the trans harness as well. We also have tabs to mount the pesky plastic fuse box on any flat surface!

http://i1204.photobucket.com/albums/bb407/HPIcustoms/HPI%20Products/IMG_8078_zpsjnsdmyyo.jpg (http://s1204.photobucket.com/user/HPIcustoms/media/HPI%20Products/IMG_8078_zpsjnsdmyyo.jpg.html)

http://i1204.photobucket.com/albums/bb407/HPIcustoms/HPI%20Products/IMG_8072_zps7nlnn5yj.jpg (http://s1204.photobucket.com/user/HPIcustoms/media/HPI%20Products/IMG_8072_zps7nlnn5yj.jpg.html)

http://i1204.photobucket.com/albums/bb407/HPIcustoms/HPI%20Products/83060b37-36b0-40ea-a1d6-2d21d5a2cd18_zpsswcvfy0a.jpg (http://s1204.photobucket.com/user/HPIcustoms/media/HPI%20Products/83060b37-36b0-40ea-a1d6-2d21d5a2cd18_zpsswcvfy0a.jpg.html)