Since this LQ4 wiring harness is a giant mess that snakes across the top of the intake and motor, im wondering if it is worth having someone "clean it up" for me. Should i just try and find a better original harness (F-body?) or can someone with experience still make it useable? I am trying to really make it a super clean install and I would be removing a few things from it anyways (A/C, DBW, Rear O2's), and relocating the Alt up high on the passengers side due to make use of my D1SC . It is a 2006 LQ4 6.0L that was removed from a GMC Sierra. Thanks for answers, I'm hoping Pocket chimes in here

 

I don't see a reason to spend extra money for a Fbody harness. The tuck harness can be dismantled and re-routed anyway you'd like. When finished, nobody should even be able to tell that it was a truck harness that was started with.

 

after you tune your ecu buy or pay to clean up your harness you can get a holley HP system with a extremly clean harness and wideband O2 for the same price and have tons of additional control over your motor without having to buy more controllers

 

Factory gm ecm will do everything an aftermarket system can and more. Just have to spend more time lengthening wires and moving things around to where you want them.

Fbody harness may fit alittle better but puts ecm near corner of passenger side enginebay. To go into car you have to extend.

Depending what you delete out, its not a bad job moving things and lengthening. Just time consuming. Almost finished on my custom ls based harness for my 89, but still sbc. Doing 24x ls1 control. I started with an fbody harness and had to add 5-6 ft to it

 

Ived used both but the holley system is FAR better than the factory and has boost control wide band self tunning fuel tables (which works amazing) 2 step and 3 step 4 stages of nitrous and the harness is extremly clean and has integrated fuel pump relay

its one of the easiest systems to install and cleanest and you just get the car started and the fuel tables will learn itself and will continueally tune

this is all for 1400 not a bad price considering you would have to get a painless harness (600) ecu (200) and hp tuners pro(750) and a wideband (400) to even come close to it

 

Yeah if you are gonna tune yourself, that system does offer lots of features. But the 411 is still a very powerful system and can do boost with 2-3 bar maps etc. Buying the software sucks as it is pricey but more ppl are familiar with that and can pay 400-500 for a good tune and be done with it. The driveability tables and fuel control plus tranny control makes oem gm stuff very good. Lots of things inside it that some aftermarket systems dont really have. I looked at the holley hp software and its user friendly but doesnt seem near as advanced.
If you can do the wiring yourself starting from used 100-150$ harness, plus 75-100$ ecm, add a 200$ wideband and 500$ dyno tune, you have a great running system for less money.

Now i didnt look at cost as much as tuning capability when i made the choice. My conversion costs more than the hp in the end but i have a local friend/tuner who knows lsx so i dont need to learn a new system. That was a plus for me. Time saved is money lol

 

If he already has PCM and harness from his dropout, that's not even a cost figure at that point. 400-500 for dyno tune, and time to re-work the harness. Holly setup still needs to be integrated into a stock harness if its desired to have factory guages work. Either way, there's no reason to buy a 600 dollar painless harness if the OP has a factory 6.0 harness. The 6.0 harness can be re-routed cleaner than a stock ls1 harness.

The holly setup is nice, but in my honest opinion, costs a little more, can't run a auto trans, and its great features for boost control and such aren't used on a typical swap.

 

Just to clear things up a little. I will be using my current TH350 (until it lets go) and then converting to a TH400. I have ZERO stock gauges since i converted over to all Autometers. I will need some type of boost control since i will be running about 10lbs with my Procharger. If i can tune everything with the stock ECU then my harness is about to go under the knife.

 

the boost control will only work with a turbo but you can have it read your boost and progressivly spray meth

and you can get the holley to work with stock gauges with a J1 harness and figuring the values needed

Or the summit digital gauges work perfect and are 36 a gauge 100 for ones with full sweep I just did a chevelle with them