Help needed for wiring harness on LS3 swap
 

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.

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


http://www.psiconversion.com/

Wiring Help
 

I can help. Shoot me a PM.

pm sent...

thanks for all the replies and help.

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

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.

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

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

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.