Roadmaster Engine swap to Elco

My son and I are building his first car. It is an 85 El Camino. Originally, the car was bought for my 80 year old dad who had wanted that "One last build". Unfortunately, he took a turn for the worse and passed away before making any real headway. The car was a good deal when taking all the AM Performance parts in consideration, but it was an under hood fire burn. We had the front cap already and many, many parts, so a good project.

HERE is where it starts getting ugly. The car had been "had" already and required a complete new body harness as the original had long been ripped out and they used a 7 circuit Highway 51 system. Not nearly enough circuits for using an LT1 from a 1996 Roadmaster and AC and all the power options. A brand new 18 circuit harness from Painless is being utilized at this point. My original plan was to utilize the original harness and controller from the LT1, but apparently I am no engine harness guy and am concerned I will be chasing electrical gremlins forever and am just not wanting to face that.

Is there any suggestions anyone can make? I also prefer to keep the LT1 harness, but not sure how to wire it removing items and modules not required.

I do not know if I am going to help or hinder you, but here goes.

I put a 454 from a 2000 C2500 in my 91 Olds Custom Cruiser. I used the original harness, and just deleted the things I did not need. I also incorporated the Holley fuel injection system into the harness, and added coil on plug ignition. It can not be more complicated than what I did on my car.

You could use an original harness for the Roadmaster, and rework the engine bay portion fairly easily. A copy of the 96 Roadmaster factory service manual would give you the wiring diagram. You are going to need the 96 computer to run the engine, because it is an OBD II system. The computer can be tuned to eliminate the accessories you do not want. The wires are all color coded, so you should be able to find and eliminate the ones you no longer need. There are people on Impalassforum.com who can give you some help with the engine harness and computer reprogramming. Since you are using the 96 LT1, stick to that engine information. The 94 and 95 are OBD I, and not directly compatible with the 96. With a 96 engine, you need the 96 trans, because the wiring is different. If you are using a stick, the only wiring you need is the signal from the VSS.

Unless the old wire insulation is cracked they should last a long time. If the insulation is cracked, you can splice them in one at a time. You can get connectors for almost any accessory on the engine. Any circuits you eliminate can be left in the cable for spare circuits. The cables terminate just inside the firewall, and you can get the firewall harness as well as all the other harnesses from the same donor car. That would give you all the circuits you will ever need. Anything you do not use just leave them in the harness for spare circuits. The only wiring you may need to add is the passenger side tail light. The AC has a specific module to run it, but if it is manual you only have to worry about the signal to the compressor, and a power wire for the blower fan. They are included in the firewall harness, but you must splice into them for your individual application. The AC has a high and low pressure switch in series with the compressor clutch. The computer uses an outside temperature sensor that only allows the AC to run if the outside temperature is above a certain temperature (can be programmed out).

You did not state what trans you are running. If you are running the 4L60E you need the harness for that as well. It should be part of the engine compartment harness. The engine requires an electrical speed signal from the trans to run the 4L60E, as an output for the speedometer, and cruise control. There should be a switch on the power steering hose to give the engine a bump when using the steering at low speeds or when stopped.

The things you want to remove are the air pump, EGR, and secondary O2 sensors.

The LT1 is a reverse flow cooling system, and you need the sealed reservoir from the donor car, or equivalent. If the engine had an original mechanical fan, you can remove the parts for that, and use electric fans. The computer can control two electric fans.

I hope that answers most of your questions, but if you have a lot more, I may be able to give you some heads up. It is not as difficult as your first thoughts might lead you to imagine. You do need a donor car to get the wiring, and a factory service manual to sort out the wires. The donor harness will actually make it easier than your first impression might indicate.

BTW, I had no help when I was working on my car. I figured it all out myself. You do need the 96 harnesses, and computer.

I would find a big table to lay the harness out on. It's not hard to remove what you don't need by carefully cutting the tape and occasionally the loom.  Electrical connector de-pinning tools are cheap and plentiful. Wiring diagrams, use the factory service manuals or an online website like alldatadiy.com.

The optispark distributor is not the nightmare that the uneducated make it out to be.

When do you plan on actually having this running by?

You should not have to de-pin any connectors. All of the OEM connectors will go to their respective parts, and the ones you do not use can be removed.

You can use 96 Caprice harnesses that have fewer wires.