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Greetings. I am a first time poster so please bear with me on this one. I have built numerous vehicle over the years, but have never done one like this. My son and I are building an 85 Elco and using a 1996 LT1 engine and trans from a Roadmaster (yes, I have replaced the Opti-spark distributor due to reputation). I have the original Buick harness and computer as well. My son is actually funding this project and does not have the money to be able to buy a $600+/- engine harness, so we have opted to use the original harness. I have researched what plugs the harness needs, but there are several plugs I am not sure of. Obviously I know we need the O2 sensors, trans plugs, power steering etc, but there are a few I am not sure of what they are for.
Has anyone out there actually used the 1996 Roadmaster harness and trimmed what is not needed? We would like to have the AC, power steering (yes, there is a plug on that one), and ultimately cruise control. We are also using Dakota Digital gauges to further complicate the situation. Again, I would just buy a pre-built harness if this were my car, but he does not have the money for that with all the other mods required to do this project.
I have photos of how I have the harness laid out and attached to plywood. I also have most of the known plugs labeled. There is a large black one that looks like it could be for ABS but not sure on that. Any help is greatly appreciated.
This is how I have the harness laid out. Note the big black plug going to the controller plugs? What is that for?
That is a perfect platform to start with for him. I started building harness' out of the oe harness' when these cars were new due to being in his spot had to work at old mans shop to buy parts.
But best thing you can do is buy a subscription to alldata all of the wiring info everything is all there in one spot. That's a pretty easy harness to do what your planning on doing with it.
You can keep the stock cruise and AC no problem and the dakota digital stuff does not add any complexity other than mounting the water and oil pressure sensors.
I'd order the dakota digital GPS speedo module it makes it even easier. The stock speed sensor has to stay in place so the tranny will shift properly
Another trick you can use to simplify things if you still have the donor car is to pirate the complete inside harness and put that straight into the elco. The ignition switch wiring and a ton of stuff is direct plug in to items in the 80s dash. You can even use the roadmaster ac panel if it's the manual controls one in your elky to control the stock hvac sys.
I would have used the original harness from the donor car, but it was an LT1 my dad had acquired years ago and never used. I did hear the engine run back in the day, so I know it is good. Great tip on the GPS for Dak Dig, I had already ordered that module with the new harnesses and controllers due to the fire under the hood for the system.
I am throwing a ton of money at this thing and wishing I had just gone carb for now, but here we are. I don't want to buy a pre-made harness because they are so expensive, so if I can get help to modify this one, it'd be great. Some of the unused circuits removed, not sure where to go from here though. Any help appreciated.
Yiou have anyone that can do the tune for you? You will definitely need that done, take out the VATS first.
I build all my own wiring, keep everything for these:
MAP
MAF
Crank Sensor
Opti
Injectors
Engine Temp Sensor to PCM
Single Wire Engine Temp Sensor to Gauges
Air Temp Sensor
Oil Pressure Sensor
Transmission(if staying electronic)
All your Gauge Signals
Alternator wiring
Front O2 Sensors
Blue and Green wires that control Fan Relays
Green with white stripe wire that is the 12v trigger to the Fuel Pump Relay
I think I got the majority, LT1swap.com has a ton of schematics.
If you can find a '96 B body factory service manual you'll find everything you need there. I found one on ebay. Not cheap, at probably around 100 bucks, but worth it IMO.
If you can find a '96 B body factory service manual you'll find everything you need there. I found one on ebay. Not cheap, at probably around 100 bucks, but worth it IMO.
Keep that main big fuse box too and power it with a #6 or cable. You can use it to supply high power connections reliably for the fans and outputs to other items like vintage air ac things like that.
IF you have the LT1 fans they work really well on a lot of swaps with OEM reliability. The parts house fans and most aftermarkets are just junk for actually keeping one cool enough for a daily driver.
If you don't have a fan I highly suggest vintage air makes a PWM brushless that is direct bolt in for a lot of platforms and highly adaptable to a bunch that it's not a direct fit for. I've used this fan on multiple customer cars very successfully and we are in south texas where temp control and ac in traffic are mandatory items in the summer.
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Need harness help!!! 
