Finally have the car gutted, stripped and ready to go. Just finished laying out and labeling all the wires.

Instead of integrating an LS1 wiring harness into my '86, I decided to go all the way and use an entire electrical system from an LS1 donor car. This way, with the dash and all going into it, it will be more of a plug and play with some of the newer features that I've been meaning to use for quite awhile, at least it will be after the newer electrical system is integrated into it.

The whole intent here is to be able to use as much factory components as possible in the older chassis. This includes SIR, ABS, and the BCM and TDS. Everything will be there, including the monsoon amp and A/C box. Essentially, the car will think it's an LS1 F-body. The car will also have hydroboost, and still look as if it were a clean stock yellow and black IROC-Z.

Powertrain is a 382ci tuned port LT1 engine that I will be running as an LS1 (custom cam/ firing order change)with the stock modified accessory drive (that was fun). At this time, while the electrical is being done, I am also considering dropping the 4L60-E and running a C5 torque tube, T56 and rearend into a custom built rear frame, though that is likely to come later.

I am curious if there is any interest out there to do a write up on this. It will be pretty time consuming and requires tearing the whole car apart, but to the best of my knowledge, has not been done to a thirdgen yet...

 

You've got my approval.

The approach on my 1991 Trans Am convertible is a little different, but similar to your project...

• gut the entire car
• install 3rd gen A/C box in engine bay
• install 4th gen A/C box inside
• install 2002 Trans Am dash, keeping instrument cluster and A/C system functional
• install 2002 Trans Am interior
• install LS1 fuel tank assembly with fully functional EVAP
• install T56 from LT1 car

I'm still undecided on the engine, but it will probably be an LT1 with 24x conversion. This will allow me to use the LS1 instrument cluster (which is driven by the data stream).

It will definitely be an electronic throttle (drive by wire) car.

I'm very tempted to install a 58x system and use the newer ECM, but that causes issues with the LS1 gauge cluster and doesn't really do much for the build since I'm not going to use a 6L80E/6L90E transmission.

Keep the info and pics coming for your build.

 

Come up with anything for front ABS sensors yet? I was going to test fit some S10 rotors and see how well those worked. I still have some research yet to do on that, but it should be fun...

For now, I'm thinking about about installing the entire box and ditching the thirdgen A/C box. Either way poses problems. With the 4thgen box, it will mate with the dash correctly so no issues there, but installing the pipes to the compressor will be a pain. If I used the thirdgen box, there are dash problems as well, but hooking up to the evaporator core will be a pain.

Choices, choices...

 

I don't plan on looking into an ABS solution.

 

Just an update.

Got my drivetrain mocked up...382ci tuned port LT1 in front of a C5 torque tube and MN6 tranny with a Z06 rearend. The crank needed to be spaced .400" and I'm not sure how to take measurements to relate the current centerline of the axleshafts with the new rear diff and measure to the front for motor mount placement. Unless it's minor, I'm anticipating a possible torque tube chop to make sure all is ok before I install the drivetrain.

I may modify the front K member to lower the engine slightly to make the drivetrain more vertical. More to follow on that later.

With the drivetrain mocked together, I was able to fabricate some custom length longtube headers to suit the TPI engine better (54" primaries to work in the TPI's powerband) that better followed the drivetrain. With the transmission relocated, there is plenty more room for longtubes under the car. I would be willing to bet that C5 longtubes would drop right in if they would bolt to the head.

A section of the passenger side of the firewall will be swapped with one out of a 4thgen to facilitate the installation of the 4thgen A/C box and related hardware. Unless I find a way to make the thirdgen box work with the 4thgen dash like it was factory, I will swap units. Unfortunately, I already did the legwork in installing thirdgen accessories on an LT1, which wasn't really that bad, but I was hoping all the A/C components would line up like stock (thirdgen accessories to a 4thgen A/C box wouldn't bolt right up, require custom lines, and a 4thgen box to 4thgen accessories will probably be too short) I want to use either thirdgen accessories with a thirdgen A/C box, or 4thgen accessories with a 4thgen A/C box.

Chassis harness looks like it'll work fine. There will be plenty of connector replacement and weeding out of unneeded wiring. Have yet to solve the ABS dilemma, but in a worst case scenario, I can always weld a tone ring to the back of the rotor and fabricate a bracket for a sensor. The rear suspension will all be C5 so there are no problems there.

Somehow, part of my LS1 harness came up missing at the house. I might use what I have an make an LS1 harness from scratch considering how much modification the stock harness would have needed anyway.

Progress has stopped until next year. I'm playing in the sandbox right now.

 

chop chop, get to it and update da' fans... ..