LTX and LSX Putting LT1s, LS1s, and their variants into Third Gens is becoming more popular. This board is for those who are doing and have done the swaps so they can discuss all of their technical aspects including repairs, swap info, and performance upgrades.

85 Z28 LT1 Swap

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Old 09-21-2018, 11:43 PM
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Engine: 93 LT1
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Re: 85 Z28 LT1 Swap

I'm not really sure, ive seen people say 500 is easy with unlimited money. I just want my car back lol 350hp/ftlb would be a very reasonable goal I think.
Old 09-22-2018, 04:27 AM
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Re: 85 Z28 LT1 Swap

Just out of curiosity, why did you disable closed loop? Is it just because you aren't running an exhaust yet?


Glad to see you got the injector issue sorted out. Ill be keeping that page book marked. I plan on starting my project sometime in October, I want to drive the car as much as possible before that but the weather is getting cooler so i suspect it will soon be time to put the car away.

Old 09-24-2018, 04:20 AM
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Re: 85 Z28 LT1 Swap

yeah im still running headers only, and the o2 sensors i have are the bosch ones that everyone says dont work correctly. i unplugged the one that was on there and it instantly improved so i left it off.
Old 10-17-2018, 02:22 AM
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Re: 85 Z28 LT1 Swap

Hey so I got doug's y-pipe and put it on and I'm very impressed with the quality. It's actually stainless steel which is a huge plus for me, the welds are nice, fit up almost perfectly, and came with all the parts needed to install right out of the box. Fired it up and with just that it sounds so much better and low and mid-range power is much better. Editing the pcm with just the headers was a good idea I think. I could really hear what was going on and with the y-pipe on there its running and driving excellent. I still don't have the o2 sensor on there yet, I'm putting it off just because I'm so happy with how it's running right now but I'm going to set it up and tune for closed loop for fuel economy obviously.

On another note I've been doing some data logging with eeHack and I'm very impressed with that program. It's excellent to see everything in graph form and can drive around a good while and see a whole range of different values and almost everything seems to be doing perfectly. Best sign I think it how the exhaust smells. Doesn't smell like fuel or burn the eyes, it's almost addictive. There are a few other subtle issues I've noticed though. The Tcc doesnt seem to be engaging. I've tried both the 94 and 95 stock pcm files trying to match the trans I have, those years differentiate the way the tcc is turned on, one is a simply on off signal and the other uses a pwm to more smoothly apply the tcc. Still unsure of the issue. I'll have to recheck my wiring and brake switch to ensure it's getting the right info but I feel like the problem is computer related, but I'm still unsure.

Overall it's doing excellent, I can cruise and it doesn't seem to be running too hard to maintain lower to mid-range speeds like it was before. I feel like some o2 sensors will help even more with this. I'm also waiting to drill and weld a 2nd bung on the headers, if anyone knows a best way to remove a small area of the ceramic coating I'm open to ideas. Tried a knotted wire wheel on a angle grinder but it didn't do much. Id really rather not grind it off if I can but whatever it takes. I''m still deciding how I want to run the rest of the exhaust. I'd like to try a different setup to avoid running pipes up over the rear diff and so close to the fuel tank. Just a little insurance if my workmanship isn't as reliable as the factory setup. Eventually I plan to weld up something and use the dual exhaust off 5th gen system I picked up just for kicks.

*Bold for the skimmers out there lol



Old 10-17-2018, 09:11 AM
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Re: 85 Z28 LT1 Swap

Are you using a 95 or 93 harness,? The 95 harness has an extra wire in the transmission plug, I believe it was for TCC lockup, if your using the 93 harness it won't be there .The 94 tune wouldn't control the lockup on the 95 transmission since it is PWM as you mentioned.

Old 10-17-2018, 09:20 AM
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Re: 85 Z28 LT1 Swap

Now that you mention it, I'm not sure, it's either a 94 or 95 harness, and I'm not sure if the trans is a 94 or 95. I'll end up sorting it out. I think the harness and trans match up, got them both from same guy I think but not 100%. I'm also maybe considering that the 94 and 95 pcm might be missing a pin or something as well, I'll dbl check. Ive never read that anywhere but with gm sometimes you can never really know without physically verifying. btw the 93 harness wouldn't have the plug to control the electronic shifting in the transmission.
Old 10-17-2018, 09:26 AM
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Re: 85 Z28 LT1 Swap

Ah right the 93 wasnt electronic control, I forgot that.

Another thing, will the TCC lockup work of the engine is in open loop? I'm not sure if these 2 things are tied together but it doesn't hurt to check.
Old 10-17-2018, 09:41 AM
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Re: 85 Z28 LT1 Swap

Yeah that's a good question, I don't see why not but maybe there's some other change needed in the code.
Old 10-28-2018, 08:30 PM
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Re: 85 Z28 LT1 Swap

Blew out one of those rubber expansion plugs i put in the extra water pump hole a few miles from home, had nothing to plug it. Limped it home, let it cool completely, drove extremely lightly until steam started coming out, stopped again, etc. Flushed it out, replaced coolant, everything seems to be fine. LT1 ftw I'll end up hooking up the heater soon anyway.

Also tore the trans mount apart somewhere. Replaced with a poly mount. Thinking about making some control arm re locators and an adjustable panhard bar.

The other post about the diffuser got me motivated to find my old one and i had also made all the pieces for another one after the first one was destroyed. I'll post some pics eventually.

Last edited by CatmanFS; 10-28-2018 at 08:34 PM.
Old 11-07-2018, 11:11 AM
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Re: 85 Z28 LT1 Swap

car looks great.What motor mounts are needed.I want to swap 97LT1 with 6speed in my 87 firebird?
Old 11-07-2018, 01:18 PM
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Re: 85 Z28 LT1 Swap

third gen v8 mounts and clamshells. lt1 has the same bolt holes on it. just replace the ones that came on the motor with the ones on an original v8 motor.
Old 11-08-2018, 07:49 AM
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Re: 85 Z28 LT1 Swap

OK,thanks
Old 11-20-2018, 11:18 AM
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Re: 85 Z28 LT1 Swap

What did you do for the engine harness? Standalone or you made your own?
Old 11-20-2018, 11:20 AM
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Re: 85 Z28 LT1 Swap

I used a 92 z28 body harness cut down and modified and mated with a 95 LT1 engine harness.
Old 11-20-2018, 05:00 PM
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Re: 85 Z28 LT1 Swap

Originally Posted by CatmanFS
I used a 92 z28 body harness cut down and modified and mated with a 95 LT1 engine harness.
How would you say the difficulty was and did you get your info from this site? Trying to decide between just buying a standalone or tackling it myself. I have my 89 engine harness and a 95 LT1 engine harness.
Old 11-20-2018, 05:04 PM
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Re: 85 Z28 LT1 Swap

Originally Posted by L98GTA87


How would you say the difficulty was and did you get your info from this site? Trying to decide between just buying a standalone or tackling it myself. I have my 89 engine harness and a 95 LT1 engine harness.
I'm doing this swap too. I'll be using my 89 Firebird harness and a 95 lt1 Camaro harness. There's lots of great info on here, lt1 swap .com and shbox .com .

I'll start a thread for my swap soon, I'm just building the engine at good point and haven't started working on the car yet.
Old 11-20-2018, 05:12 PM
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Re: 85 Z28 LT1 Swap

It was terrifying to start, but with some good diagrams and a solid understanding of basic DC electrical stuff its really only a matter of supplying power to things, ground to others. I cut out everything I didn't want or need from the car like power accy and ac crap. Made sure to keep the ign switch and main power wires(red,pink,purple,yellow, etc), used the leftover wires from the fuse box and ignitiotn switch to supply power to everything on the engine, ecm, tcc, inj etc. Just adapt the car harness to give the engine the fused connections it expects.

Lt1swap.com and shbox.com has all the diagrams you'll need. Just study them and break it down. To get it running there's only about 10 wires you really need to connect between the car and eng. Hope that helps, I'll give you exact instructions if you're going to try it on your own.
Old 11-20-2018, 05:25 PM
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Re: 85 Z28 LT1 Swap

If ypure looking for an easy start up remove any starter relay and wire directly from the ign switch starter wire->trans park/neutral switch--> to your starter. Now use the big pnk ingition coil supply wire coming off the ign switch to go to a little autozone fuse panel, set that up so your ign coil/inj1/inj2/etc supply for the eng have thier own fuses at the right amperage to match what the lt1 setup is expecting. I used another small fuse panel for pcm fused power, a fused brake switch input, and a fused park/neutral input. After disabling vats it should start up.


Old 11-20-2018, 08:30 PM
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Re: 85 Z28 LT1 Swap

I've read a few diagrams and even watched a video by LT1swap.com and it doesn't look all that bad. Mentally it's easy for someone to see what's involved and say nope. I'd like to give it a shot. I have yet to actually begin my swap but I have both vehicles and everything I need, was just stuck on wiring. Any help you could provide would be immensely appreciated.
Old 11-20-2018, 09:11 PM
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Re: 85 Z28 LT1 Swap

Yeah it's really not bad once you have a plan. The idea is to leave most of the car harness alone, from the battery the main power wires go to the starter and over to the c100 plug on the driver side firewall, also the body harness for the headlights and taillights should remain untouched. leave this stuff alone, and truncate and tuck back the extra wires for the engine related things, i dunno what the harness for the engine youve currently got in the car, but the older style really only had a handful of wires that can sometimes be repurposed to serve the new engine. I cut the hole where the ac wires come out a little bigger and was able to hook up the engine harness for the lt1 and sneak the plug wires for the ecm through this hole. All the communnication between the car wiring and the engine harness can be done inside under the dash so you don't have a big mess in the engine bay.


Old 10-16-2019, 06:33 PM
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Re: 85 Z28 LT1 Swap

I'm doing an LT1 swap in a 3rd gen as well. My car is a 92 formula that was originally an L98. I just modified an LT1 intake to accept a distributor and plan on using the TPI harness slightly modified.

96 corvette LT1
LT1 Distributor mod
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