So four months without a Thirdgen and I'm busy planning, plotting and doing bench builds in my head as I try to go to sleep! ...Whatever I find will likely NOT keep it's engine for more than a season or two. Thought about buying a clean unmolested survivor but that's just not me. I need a project. With my Iroc, many of the problems I ran into were related to wiring, and I think a lot was my trying to seperate the two harnesses of my 89 Iroc. Everything was fixable of course, but having the engine and chassis harness wired together was a pain for sure. My years on the boards have told me that the 85-87 engine and chassis harnesses are seperate. Am I correct in remembering this? Can you simply remove the engine harness if you're going with something new? LS? Holley EFI? A carb!? A 88-92 would absolutely NOT be a deal breaker, but having that seperate harness would sure be nice.

 

The separate harness sucks in it's stock form. Specifically because you often have two bundles of wire cramped into a tight space. On the later cars everything is just cleaner and more refined from years of development. You couldn't hardly give me an early thirdgen. 89-up is where it's at.

 

I get that, but my thinking isn't to live with it day to day, but to remove it. Whether I go LS, or just build another modern SBC, I'll likely control it with something not OEM. ...and being seperate would sure make that easier. -or at least that's what I'm thinking.

 

It's not just the harness I'd be thinking about, it's the rest of the car. You can put a modern drivetrain in a 85-87 Camaro, it's still going to have a ton of other subassemblies that aren't as refined as the later cars. There isn't that much about the harnesses being integrated that should be all that hard to work around. Coming out of C100 you've still got the lights on their own harness, and the engine harness separate. Compared to the rest of an LS swap, the few wires you might need to replace from the original engine harness are minor. It just doesn't seem to be a problem. But that's just my opinion, FWIW.

 

I can appreciate that. -I'm no expert, and I just felt that while trying to wrap my head around all that wiring, NOT being able to seperate it physically was just difficult. Again, I'm no expert, I guess I just had trouble with it.

I definitely get THAT point for sure.

 

Lets see,.............

This is a 90 TPI ENGINE / ECM harness


The thing is HUGE, basically the same ( size) from 88-89.

87 IROC (TPI) ENGINE harness:


This is all that's needed to run an engine; Starter, Alt, Distrib, Gauges, Wipers, & HVAC. It uses the 84-87 style wiper and I think 88 can be converted to work OK. Unless you working on an 82-83,....... STAY AWAY from 82-83 ENGINE harnesses; those years have different Power Distribution systems and a Wiper system that's specific to the firewall and wiring of another 82-83. (Power can be re-pinned - but your still dealing with the Wiper system.)

86 IROC ECM harness:


The ECM harness is about the same (size) in all 84-87 V8's. ( carb is a bit smaller) If your changing the induction from what-ever it is to something else,..... NONE of this is needed. There is usually enough power ports available in the fuse-box once the ECM harness is pulled ( Injector fuses, Fan fuse, ECM fuse, ect ) for most things that would be getting re-installed; EASILY enough to get it running. If you've got other things to add ( Electric water pump, Fog Lights, Duel fans, ) An auxiliary fuse-box is simple and very easy to make - in any size required - IF needed at all.)

When I write on these boards to members about harnesses I always capitalize the type of harness it is so that it STANDS OUT that the 84-87 harnesses are different parts and separate from each other. There are minor changes from Carb to FI ENGINE harnesses ( oil pressure wire, CHOKE wire, etc ) but they are minor and easily dealt with.

IMO : Quicker to get the wiring for the engine done and over with quick so you can check it off the 'to-do' list & focus with the new induction system.

 

Don't let a little plastic wrap and wire loom slow you down. It's a bit of a mess but honestly at this point, I'd probably want to remove the old rotten split loom and dirty harness tape anyway. From there it's just a matter of studying the diagrams and depinning what you don't need. By integrating your engine harness with your EFI harness the result is cleaner.

What John's example doesn't show is both the harnesses from an early car next to the single harness in a later car. It's the same quantity of wiring. Just one way it's in two looms, the other it's in one loom.

It's really not that bad, I completely stripped all the airbag wiring out of my 91's dash harness. I had to get in there to wire in the 4th gen BCM, and convert from auto trans wiring to the T56. I get to do something similar to add the wiring for the T56 to the engine harness. Still debating modifying an auto, 5spd, or the original 3.1L harness, doesn't matter much since I'll be ***** deep in the harness regardless.

Having a functional working knowledge of the wiring in a project car, much less an engine swapped car, isn't a bad thing to have.

 

I'd almost blocked out the memory, but a similar wiring odyssey was the other project...





Converted from a feedback carb system, to turbocharged EFI, with a Thunderbird harness into the Mustang. Also got to rewire the external regulator, and starter solenoid, from the passenger's side to the driver's since the EFI cars had the battery relocated.

Point is that wiring really isn't as bad as it seems. I can do it, and I'm an idiot.

 

I appreciate the feedback from both of you guys. ...and just to be clear, I'm not saying that seperating the two IS or should be a problem, I think I just had a mental block in my head for some reason. ...and honestly I don't really know what I'm gonna go with yet. SOOO many ideas floating around in my head. I'll likely go back and forth until the day a smokin' deal lands in my lap and I'll end up bringing it home.

The wiring was one of the first things I did after pulled the engine, however by the end of the project, I was a lot more comfortable with it. I imagine doing it again wouldn't be nearly what I've made it out to be.

 

I'm learning about these cars as I go, and I am no stranger to wiring conversions and dash swaps. I have two cars and I am wanting to merge the two as one. The first is an 88 Iroc 5 speed, but it is an Illinois car so it is too rusty to safely have on public roads. The second is a 91 Z28 that is 100% rust free underneath, just minor surface spots. I want to create something never built which is a 91 Iroc. I have a 145 cluster for the 88, and I despise the yellow of the 90-92 interiors have but love the 91-92 exteriors. My Iroc is a 5 speed, and the 91 is not.

The obvious differences are mass air vs speed density, I have a brand new motor (355) ready to drop in that came with the 88. The end point of my ramble here is, I want to go backwards to a degree and run the 88's interior dash and all in the 91. Now since I have everything from both cars, it should be as straightforward as it can get, am I correct? My questions circle around the engine and dash harnesses, so aside from being told I'm insane to go backwards seeing as most people go forward with upgrades, this is still something I want to do.

 

This is from entire car swap experience. I had a 90 RS 5spd that had a bent right side sub frame. I found an 86 Z28spd Roller for $200. This was back in 2001, days before 9/11. Anyway, while doing the 90 interior swap I discovered that the Firewall brackets that the Dash attache to are in different locations. So, when you do the swap, make sure you take that into account.

 

Learn to love the 90-up dash. Aside from the lame airbag, it's better in every way. A quantum leap in technology and build quality, better than the 82-89 dash. It's almost modern, and nearly as good as a 86-92 Firebird. I understand personal preference, but from personal experience, the 82-89 Camaro instrument cluster is pure garbage. Get away from noisy jumpy cable driven speedometer, the edge lit gauge faces, the flaky gauges in general...

 

Maybe if I could find a 145 speedo for the 91 that didn’t cost a small fortune I could live with it, because I believe a sports car should have a real cluster not something that a v6 can do. I’m not saying I would go and try to max it out, but I guess I’m spoiled, I mean hell my 2014 Sierra has a 140 cluster, so the 115 seems lame to me in the Camaro.

I did like how the 82-89 tach started at the bottom and swung up like the firebird did, I don’t know, I guess I’m weird.

 

I’m familiar with brackets in different places, because I did a 95-98 dash swap in an 88-94 GM truck last year, so that doesn’t scare me away, it just adds to the reason of buying a welder that I already wanted to buy to begin with.

 

Don't let anyone ever tell you want YOU want. Swapping dash housings is pretty easy, don't even need a welder - just install nuts/bolts in the spot weld holes after drilling out the old brackets then set the correct dash brackets in place and your G-T-G.

https://www.thirdgen.org/forums/inte...dash-into.html

The "trick" here is the wiring. Your best option ( IMO ) is to remove ALL of the wiring from the 88 and install it in the 91. I mean EVERYTHING. Might seem like a lot of work but when you consider the time saved compared to trying to find all the wiring conflicts - you'll be ahead of the game by just swapping it all. MAF vs SD, Auto Vs Manual, Cable vs Electric Speedo,... you can forget about dealing with any of the conflicts that will occur by simply swapping ALL the wiring. There will be some minor problems - like the 3rd brake light, - but they can be dealt with on a 1-by-1 basis.

 

I figured it should be that easy, and considering that the wc t-5 is a cable drive speedo setup, eliminates the need to track down a vss. Third brake light should be just extending the wires, so that is no big deal there.

I appreciate the pep talk, that’s always nice to hear.

 

No Problem !!

You should start your own new Thread so we can see your progress and learn from it. Good Luck !

 

140mph clusters for 90-92 Z28s are out there, it just might take awhile to find one that doesn't cost an arm and a leg. Looking for the missing piece is part of the fun of the hobby.

While you can use the earlier wiring in a later car, virtually everything in the later car will have substantial upgrades over the earlier car's parts, including the wiring harnesses.

Personally I've owned an 83, 84, a pile of 86s, an 87, an 89, and a pile of 91s, and the earliest thirdgens I would want to be stuck with, are 89s. Everything in the later cars is just better thought out, easier to work on, more dependable. GM really didn't start getting it right until 89. You'll do whatever you want to do, I'm just giving you advice that you're going the wrong direction, based on what I've learned about these cars in 25 years. What you do with that advice is up to you.