84 engine swap questions (Page 1/2)
cartercarbaficionado AUG 20, 07:42 PM
so I picked up a spare v6 and have been wanting to install it Into my 84. it is a gt rear harness I was planning on removing the gt stuff for and giving to someone who needs the taillight wiring and then splicing into my stock wiring
now the thing I'm unsure of is how my new v6 wiring will work with the 84 wiring or if I need to rip out the entire interior to swap a 86 harness into. it's really just the c500 since I'm not actually sure how or where the 84 has its main connector.
another concern is the transmission which is an automatic and I would like to keep it but have been told the i4 and v6 autos are different and I would need to convert a manual harness to a auto harness and note the changes since a manual swap is in this one's future
Dennis LaGrua AUG 20, 08:53 PM
Outside of the torque converter stall speed all Fiero TH125h automatic transmissions are the same. As for bolting a 2.8L V8 into your 1984 Fiero; you use the motor mounts but new motor mount brackets will need to be bolted to or welded to the cradle.Trans mounts may be the same. Easier bolt in job if you use the V6 cradle.
As for wiring use the 2.8L harness for engine control and just keep the existing wiring for lights, gauges, cooling fan , VSS etc. Its not a hard swap but you will need some rewiring. You will also need the V6 ECM and the mounting tray. The 84 tray is different,

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

cartercarbaficionado AUG 21, 01:46 AM

quote
Originally posted by Dennis LaGrua:

Outside of the torque converter stall speed all Fiero TH125h automatic transmissions are the same. As for bolting a 2.8L V8 into your 1984 Fiero; you use the motor mounts but new motor mount brackets will need to be bolted to or welded to the cradle.Trans mounts may be the same. Easier bolt in job if you use the V6 cradle.
As for wiring use the 2.8L harness for engine control and just keep the existing wiring for lights, gauges, cooling fan , VSS etc. Its not a hard swap but you will need some rewiring. You will also need the V6 ECM and the mounting tray. The 84 tray is different,



I actually don't even have the 84 ecm tray do I'll grab one. I already have the ecu and funnily enough I have the mounts for the i4 to v6 cradle conversion. trans mounts are just as simple as choosing another hole on the frame made for it (I also have a 85 cradle just not looking yo swap that in yet)
so I can't make my gt harness convert into the stock 84 harness thats almost standalone?
also a full guide would be awesome since if it's alot of work I'll just do a 3800 or 3.4 dohc swap instead.
Mickey_Moose AUG 22, 03:08 PM
The 84 wiring is completely different and not as straight forward as the other years.

The C500 connector on the 84 is between the engine and the firewall about in the center.

You have 2 options:

1) build your own harness (basically splice the 84 and the V6 together - plus you need to add extra wires (V6 uses 2 power feeds for the injectors - the 84 only has the 1 feed, so you need to add wiring and connector into your fuse box to add another fuse).

2) get the whole harness for the V6 from the engine to the ECM (you still need to add the extra injector wire/fuse) and install.

You could also "Mickey Mouse" the injector power feed by splicing the 2 together - but I wouldn't.


IMHO you would be better off installing a 3800SC (or other) as the wiring would be the same amount of work - or just sell it and buy a V6 car.

[This message has been edited by Mickey_Moose (edited 08-22-2024).]

Dennis LaGrua AUG 22, 03:37 PM
I believe with the amount of work and rewiring required to install the 2.8L V6 in an 84; an engine swap is the better way to go. Its a bit hard to find good easily swapped engines like the 3800 but the 3.4L TDC is less in demand may be cheap and easy to find. The venerable 4.9L Cadillac engines could be found in abundance several years back but even those have dried up.
If you want a more challenging swap the LS4 might be good for you; lots of work but over 300HP.. The early Ecotech engines are also a choice as mod parts, swap parts and ready to run plug in harnesses are available.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 08-22-2024).]

cartercarbaficionado AUG 22, 05:30 PM

quote
Originally posted by Dennis LaGrua:

I believe with the amount of work and rewiring required to install the 2.8L V6 in an 84; an engine swap is the better way to go. Its a bit hard to find good easily swapped engines like the 3800 but the 3.4L TDC is less in demand may be cheap and easy to find. The venerable 4.9L Cadillac engines could be found in abundance several years back but even those have dried up.
If you want a more challenging swap the LS4 might be good for you; lots of work but over 300HP.. The early Ecotech engines are also a choice as mod parts, swap parts and ready to run plug in harnesses are available.


probably gonna do a 3800 even though I really don't like that engine (sound and the many recalls that affect the ones I can afford from junkyard) ironically it's easier to find a 2000s era Northstar than anything else around here but that is quite a bit of work to put into a 84 and not a whole lot of fuel economy.
only reason I considered a 2.8 swap is good fuel economy and a quad 4 swap is just as much work as any other
82-T/A [At Work] AUG 23, 07:49 AM

quote
Originally posted by cartercarbaficionado:

so I picked up a spare v6 and have been wanting to install it Into my 84. it is a gt rear harness I was planning on removing the gt stuff for and giving to someone who needs the taillight wiring and then splicing into my stock wiring
now the thing I'm unsure of is how my new v6 wiring will work with the 84 wiring or if I need to rip out the entire interior to swap a 86 harness into. it's really just the c500 since I'm not actually sure how or where the 84 has its main connector.
another concern is the transmission which is an automatic and I would like to keep it but have been told the i4 and v6 autos are different and I would need to convert a manual harness to a auto harness and note the changes since a manual swap is in this one's future




There is a guy (on the Reddit forum) who swapped in a Fiero V6 into his 1984, and is literally running it with the stock 84 ECM and TBI unit. He installed an Edelrock intake and basically just bolted a plate onto the top of the square bore, cut a large hole in the middle... bolted the factory TBI unit to the top, and he says it's running great.

Literally factory ECM and everything... including the stock ignition system too. I'll see if I can find it...


Yup... here you go: https://www.reddit.com/r/fi...he_stick_wiring_and/
cartercarbaficionado AUG 24, 03:36 AM

quote
Originally posted by 82-T/A [At Work]:
There is a guy (on the Reddit forum) who swapped in a Fiero V6 into his 1984, and is literally running it with the stock 84 ECM and TBI unit. He installed an Edelrock intake and basically just bolted a plate onto the top of the square bore, cut a large hole in the middle... bolted the factory TBI unit to the top, and he says it's running great.

Literally factory ECM and everything... including the stock ignition system too. I'll see if I can find it...


Yup... here you go: https://www.reddit.com/r/fi...he_stick_wiring_and/



this is why your the best. looking into doing a similar thing with a 3.1 or 3.4 or maybe a cheap lq1 now
82-T/A [At Work] AUG 24, 01:00 PM

quote
Originally posted by cartercarbaficionado:

this is why your the best. looking into doing a similar thing with a 3.1 or 3.4 or maybe a cheap lq1 now




Hah, no problem. That's one of those things that, once you see it, you never forget it because it's so wild... and you're like... duh, why didn't I think of that?
cartercarbaficionado AUG 24, 09:19 PM

quote
Originally posted by 82-T/A [At Work]:
Hah, no problem. That's one of those things that, once you see it, you never forget it because it's so wild... and you're like... duh, why didn't I think of that?


ironically I did think it was possible but didn't want to hack up the harness for a theory since it's a decent car. buuut now that I know I'll be relocating the stock c500 to the later location and lengthening the harness in preparation for a later v6 swap