I am in the middle of an LS1 swap on a 1985 Z28 TPI. The TPI was originally swapped with a simple carbed setup (older 350), which is how I purchased the car, and have removed that and have begun installing the LS1. Little did I know, there is no ECM, nor is there a "regular" harness from the ECM into the engine bay. No harness through passenger side grommet, no "white" side of C207 (only the two black connectors, and the small grey C221). I didn't really suspect this originally, because all gauges are still working, and I was under the impression portions of the gauge inputs came through that connector. I should also mention that the C100 portion of the connector is there, it simply ends around the blower motor and evap box connections.

Is this perhaps how the carbed setups were? I don't mind getting my hands dirty but I am sort of confused where I should even start. If there is a "go to" way people typically swap back to an old carbed setup, I would love if someone aware of this and could shed some light on what I'm most likely dealing with. My guess is either:

A. It's a carbed third gen harness that doesn't have the portion going through the fender. Or
B. The previous owner got creative with regards to the more acceptable ways of wiring.

This is also my first post, thanks to everyone who has contributed so much to this blog. It's awesome.

 

Just a follow up to this, I have recently discovered that there are apparently two separate harnesses for my year, where most of my research was apparently focused only on 90-92 which have one complete harness.

This would explain why there simply isn't that portion I was expecting. However, a problem remains, as my repair manuals, and wiring diagram links on this forum both act as if the 1985 model never even had a TPI. Does anyone have any info related to specifically the 1985 model year, and what direction to go when swapping? If there is a way to just run everything through C100 I think that would be ideal.

 

The earlier cars all had a harness that came through the pass side kick panel, kind of above the passenger's right knee; and from there, up into the engine bay from behind the wheel well liner. There is a hole about 4" square that it passed through. Both carbed and EFI. The basic "car" and "engine" - lights, charging & starting, gauges, ignition, wipers, etc. - were wired just exactly like cars have always been wired, through C100 or the like. The entire computer control system was a complete separate stand-alone add-on, not integrated with the "car" and "engine" wiring.

AFAIK there aren't enough terminals in C100 in such a car to run a whole EFI system. I don't think I'd try that.

Not all that many connections have to pass between the engine and interior though, if you locate the LSx ECM outside the cabin, like it normally comes in those cars.

 

I don't wish to run the entire EFI system through C100 haha. I mean't "everything" with regards to what I perceive to be missing from C207 not being found in my car.

So just to clarify, I have the other side of C207 (black connectors) and C227 just dangling near where the computer would normally be. No computer, and no white connector side of C207. I was under the impression that things like MIL, speedo, inj banks, ecm, park/neutral switch ran through this.

If I understand you correctly, you're saying these run through C100 on the 85?

Do you happen to have a diagram for this? Both of my repair manuals act like TPI didn't exist on the 85, and so do the wiring diagram repositories I've seen on this forum.

 

Your speedo is mechanical; the old cable drive. No wires.

Neutral safety switch is entirely inside the car. On the shifter. The solenoid wire comes through C100 after all that. Like a 50s car.

MIL is entirely inside the car. The ECM was under the dash on the pass side; who knows, might even still be there; the lamp driver is in the console.

Injectors and all other ECM wiring like sensors etc. went through the windshield cowl as described. Totally separate harness. Acoupla plugs plugged into the main car harness; like, to get its 12V. Not really a whole lot of them though.

No I don't have the FSM for 85.

 

Yes the speedo is mechanical, any suggestions on a cluster swap? I believe the 90-92 are electronic, but don't fit. Not sure I'm thrilled with the idea of spending $500+ on new gauges lol. Any advice there would be much appreciated.

And I understand that the MIL is inside the car, I guess I'm confused how I should go about integrating the LS1 swap with it, as I only have the black connectors dangling, (no ECM, no C207 white connector as mentionted before)

I've not been able to find the windshield cowl harness as mentioned. You're not referring to the harness that would come through just behind the fender correct? That is the one I stated before that is missing. Or perhaps my 85 wasn't designed that way, as I have learned it is somewhat of a bastard year.

I'm thinking I will just run the LS1 pcm standalone, and attempt to mount the PCM in the stock location by making a hole below the evap box.

I was able to track down a 1985 firebird service manual. Hopefully that will help with some of the wiring.

 

No, 90-92 are still the same mechanical type gauges as the older cars, except for the speedo which is electronic. To get a VSS in your car, they put a little optical device on the back of the cluster, that literally looks into the speedo and watches the part inside there that the cable spins. It gives 2000 pulses per mile... the thing that spins is a bar, and it makes 1000 revs per mile. It's a little yellow box with a 3-wire pigtail hanging off of it.

85 was in fact designed with the separate ECM harness that passes through the kick panel into the windshield cowl area and from there through the fender. It wouldn't really do you much good anyway, it's really no great loss that it isn't there. I suppose if you want to mount the ECM inside the car you could run the wiring through that same path but you'd probably have to extend every wire about 6 feet. There's nothing about 85 that's really all that different from any other year around it, except for some of the details of TPI itself, which of course aren't a concern at this point anyway. A Firebird manual isn't going to be quite the same as your Camaro, so you'll still have a good bit of figuring out to do.

As far as "integrating", you are probably going to have to do pretty much the same thing anybody would do with any older car. The existing oil pressure, coolant temp, and voltage gauges can easily be piggybacked onto the motor. Not sure myself about the gas gauge or the tach, or the MIL as far as the details, but I can't imagine it being too complex. You can send the existing VSS signal to the LS ECM and have your tuner set it up for the 2k pulse/mile signal.

 

My 84 was originally a carb / automatic and when I installed an LT1 the car had very little wiring needed for the conversion. All the gauge wiring in my ride was fed into the car thru C100; Your car is TPI so there is no Lamp Driver and the Oil Pressure gauge wiring *might* be fed thru C207. I ended up installing a custom built Relay center/ Fuse-box to add the electrical systems I needed to get everything working ( duel Fans, electric water pump, electric fuel pump, Injectors, PCM, etc... ) My ride had a factory electric Speedo and I used a Dakota Digital box to re-calibrate the T56 speed sending unit so it was compatible with the factory 84 digital cluster - as well as an aftermarket Speedo head. I also cut/spliced a 1995 ALDL into the wiring so I have a working CE light and could plug a programmer or code reader in.




Here is the C100 schematic for the 85 Camaro:

https://berlinetta.info/media/shopma...00Camaro85.jpg

Here is a diagram I made showing the C207 and C221 connections for the 85 Camaro. ( dash harness to ECM harness ) Should be enough info there to help get you started !

 

@sofakingdom

Do the 90-92 gauges not have electronic inputs? I was under the impression the main difference between them and the earlier gauges, was the change from mechanical speedo to electronic speedo (connection wise, I understand they technically had different gauges and visual displays). Which is the focus of what I was saying. I'm not under the impression they are digital if that's what you're assuming. I also understand how the optical sensor works. I'm not sure why I would have my "tuner" program anything, since there won't be anything to run the cable speedo anymore. Hence why I'm trying to familiarize myself with options to replace it other than dropping money on a whole new cluster setup, which sounds like what most people do in this situation.

And as far as the harness goes, just to make sure I'm not confused here, you described to me exactly what I already stated was missing? Sort of confused there.

@John in RI

Funny you should mention, I was just thinking to myself last night "if I only had a berlinetta cluster", because the diagram I had showed the "electronic cluster" was expecting a 4000ppm. My 1985 Firebird manual shows the same connections at C100 your camaro one does (for TPI).

This should mean that everything is accounted for except the speedometer. Not sure what to do there. Paying $200-$300 for an electric to mechanical speedo adapter seems really stupid tbh.

Thank you for the diagrams. Is the "berlinetta.info" repository yours personally? I see there are a ton of other diagrams in that directory, but I don't want to poke around too much if it's not necessarily public.

 

No the 90-92 gauges are not electronic; they are the same simple electrical system as earlier cars. Except the speedo.

My comment about having your tuner (yourself, whoever) set up your vehicle speed at 2000 ppm was in case you were planning on using an existing transmission. If you use a 4L60E or T-56, it doesn't apply.

Some of the 85-92 cars with the VSS in the transmission give a 4000 ppm signal, some 2000. Depends on year and induction system. Pretty sure all the TBI cars were 4000 but the TPI and some of the carb cars changed from 2000 to 4000 at some point, but don't quote me on that. I don't think the FSM goes into any detail about it.

C100 is fairly generic. Lots of cars were very similar there, for the simple reason that the stuff that it carries is largely universal. Not just these cars, but the whole GM product line, for many many years. Headlights, starter, ignition, gauges, etc. are the same no matter what body style, over a long period of time. Most of the stuff that varied from car to car - cruise, HVAC, and so on - has its own stand-alone harnesses that run separately.

If you use a later transmission such as the T-56 with its 17000 ppm speedo signal, you could use an adapter such as the Dakota Digital that John mentioned, to give the 2000 or 4000 ppm signal your speedo would need, if it had been electronic to begin with. Which I think John's car was, which is likely why he handled it the way he did. Firebird went to electronic speedo before Camaro in at least some models; 85 for TPI cars and maybe some of the others. There also is, or at least was at one time, a box that's basically a little electric motor that spins the cable, that can convert from an electronic signal to a mech speedo. It was kinda spendy though. It would be set up to give one rev every x pulses it received.

I got confused about what was and wasn't present in your car. Sorry about that. And yes, the TPI and carbed cars were wired very similarly; the ECM harness, and the engine half of C100 (the half with ign, starter, alternator, gauges, etc.; the car half has headlights, horn, wipers, etc.) came to the vehicle assembly plant installed onto the motor, and the final assembler routed the one into the cabin and made the connections inside there, and plugged the other up on the firewall. They didn't stand over the car as it went down the production line trying to hook up all the stuff that plugs in all over the motor. I would urge you to go visit an assembly plant sometime, one that gives tours that you can actually watch cars being built; it's an AMAZING experience, and helps one understand where the car comes apart and where the interfaces are and that sort of thing. The Vette plant in Bowling Green may still do that. Just like, they didn't lay up under the dash the way we might, and plug all that stuff in, from behind; instead, the dash came to the assembly plant from the plant it was made in, with all that wiring already on it, all the way down to the fuse block and the interior side of C100. It comes back out the same way: acoupla plugs to the radio & speakers, the 2 to the ign sw, the ones to the steering column and dimmer switch, the one to the HVAC (a single wire that brings it 12V), and the one for the MIL, the speedo cable, about 5 or 6 bolts & nuts, et voilà.

 

Yes,... Berlinetta.info is mine.

If you click this link you will see all the diagrams I've got the the "Shop Manual" directory; feel free to browse. There's a bunch of diagrams in there, mostly thirdgen but some Trailblazer stuff too. https://berlinetta.info/media/shopmanual

There is also another folder that might have some interesting stuff too; I try to leave files in a "help" directory because I've linked to these files in the past for people all over the world and want to keep the pictures visible on the web long term. https://berlinetta.info/help

As far as your Speedo concerns,..... the VSS converter/adapter might just be the least "painless' option ( no pun intended ! )

https://jagsthatrun.com/collections/speed-sensors

 

Thanks for all the help guys. I'll be building a custom gauge setup. Harness is already apart, and I'll be taking care of fuel level / cpp separately it seems. Not having the white side / harness of C207 certainly doesn't help, but nothing a new connector and some wires can't solve. Thanks again guys.

 

It would probably cost $5-6 to ship one to you,...... Send me a PM if your interested.