Better to get a premade wiring harness or get ur old one cut down for swap?

[69greyghost]

Hey guys I am really close to doing my swap and had a question about wiring harness' to use. Is it better to get a premade wiring harness from a company or better to get the original harness for ur car cut down by a local shop that you know does a good job. I have my harness already and know a shop that cuts them down for a good price, I was just wondering if there is advantage of either selection. Thanks in advance guys.

[IndyNova]

I'm doing a swap in my nova now, and I'm getting my orig harness re-wired. It's cheaper than buying one and he's putting ev6 injector plugs and making it 3' longer so I can mount the ecu in the car as opposed to the eng bay

[69greyghost]

I'm doing a swap in my nova now, and I'm getting my orig harness re-wired. It's cheaper than buying one and he's putting ev6 injector plugs and making it 3' longer so I can mount the ecu in the car as opposed to the eng bay



Do you suggest I have mines made longer like yours? The shop that does them is reputable, I know the owner. He has done countless ls conversions, and does this for others that want to do theyre own swaps. I am not concerned about his work, I am more concerned if I am losing anything by having him do it as opposed to buying a premade harness, if there is no advantage or disadvantage either way I am gonna let him do my harness.

[IndyNova]

That would be your call, I know I don't want all that wiring to be seen in the eng bay. My only issue is that with the size of the connectors, making a hole in he firewall that will fit the connectors and not look like poo. I don't think that there is really any advantage one way or the other as far as buying one or having one re-worked. Just my .02, but I'm still a noob at the ls swaps

[gnx7]

Here is my take on it:
Stock LS engine wiring/PCM
$300-400 for a used harness with PCM
$300-400 to rewire it
$400-500 to have it custom tuned (then keep paying for add'l tunes if you make changes)
Total: $1K-1300

Holley HP EFI
computer with brand new LS engine harness plug/play
Load up a base file map and learn to tweak it yourself
Allows for 2 step launch control, data logging, lean cruise, e85 maps, optional traction control, boost controller, nitrous controller, engine shut down for too high of coolant temps or too low of oil pressure
$1400

[sshep71]

The aftermarket plug and play systems have their draw backs as well. They all use proprietary programming and coding which makes it a B***H if you ever want to add/change gauges, and do reprogramming. You need their and only their system to reprogram and adjust the tune. Some dyno shops wont work with their software because of this. Also what transmission are you going to run? I know that there have been some complaints on various boards about people running into problems with the programming communicating with their transmission.

You can send your stock harness to John at Speartech and have him rework it for under 600.00. Plus the tune on your ECU for an additional 300.00. After he does the rewire he will run your harness on an engine he has to make sure it is good to go. There is a lot more support and knowledge about the stock ECUs and their coding than the aftermarket stuff. Just something to think about!

[Black93GT]

If you have the capability to properly do the harness yourself then go that way. Buying new is more $$ but will save you time and any headaches. Having someone do a quality rework is certainly a $$ saver.

Honestly, if your harness has been hacked and is questionable..... just buy a new one. One of the harness I'm doing right now was badly chopped and missing the transmission connections. which doesn't help connect it to the T-56. Now we'll have to order the plugs... and they can get pricy.

[gnx7]

Here is another testament for the Holley:

Example: 101mm Turbo LS V8 running 500lb Moran injectors. He gave up on the factory computer after wasting many many hours trying to get it work.

Wired up the Holley.... loaded in a base file.... badda bing... badda bang. It runs and says it idles as good as it did with 80lb injectors!

Dyno Tuning in 1 week. HP estimate is 1200rwhp.
Read post #178
http://ls1tech.com/forums/forced-induction/1615560-update-dyno-day-9-18-methanol-403-lsx-torque-stopper-intake-101mm-turbo-87-gn-18.html

If you don't want to pay a tuner $400-600.... look into the Holley.

IMO mail order tunes are great to get a car going... but to eeek out all the available power you need a real tuner to make tweaks.... or run a system like the Holley to do it for you.

I hate electrical and had mine all wired up in around 2 hrs. The only thing already mounted in my car was my battery and cables going for battery ground and + cable to my starter/alternator.

[69greyghost]

Mark you are one good salesman!

[Sparks67]

That would be your call, I know I don't want all that wiring to be seen in the eng bay. My only issue is that with the size of the connectors, making a hole in he firewall that will fit the connectors and not look like poo. I don't think that there is really any advantage one way or the other as far as buying one or having one re-worked. Just my .02, but I'm still a noob at the ls swaps

You have to do cannon connectors, that is best to put it through the firewall.
If you look at Camaro XV, Mark has it by the battery tray.