Well, I am starting a thread to document my swap and ask questions. I am very new to the fiero community and engine swaps in general. I am mechanically inclined enough to do my own work and am familiar with 3800s (my daily is an 04 lesabre). I am a college student so trying to do this as cheap as possible. Will be learning to weld to make the exhaust.
My car is currently an auto but I am getting everything for the manual swap but pedals and shift assembly for pretty cheap. (Does anyone have a manual brake pedal and clutch pedal or 5speed shifter assembly laying around??)
So far I have a harness for a 3800 auto swap that I got from a junkyard. Can I just leave the auto trans unplugged? I will also have to acquire a flywheel. Does anyone around here make those for fairly cheap? (west coast fiero's are $400 and way too much for me)
I have emailed zzp asking about a tune for the ecu. To delete vats, the auto trans, and the like. Waiting for a response.
From what Ive seen this should be a simpleish swap? Can use stock trans mounts and axles since its a stock transmission, I now have a front mount from that junkyard swapped car. Fabbing the exhaust will be my greatest challenge. And lifting the car... Anybody got tips? Ik something custom will have to happen for the speed sensor. Also, how do people go about the rad fan, temp guages, rpm guages, oil pressure guage?
All progress or things done to my car will be described here.
Pics of car:
------------------ Thanks! Nathan Shade "The Cheese Wedge" Yellow 86 GT 2.8 auto with a blue roof.
IMO the 3800 is still a good swap. The engine is certainly dated but later generation engines that GM designed don't seem to have the same reliability record. I would consider leaving the 4T65e automatic as its a far simpler install better matched and far stronger fo the power of the newer engine. The Getrags are getting hard to find and are very expensive when you find a good one. The harness will need to be a combination of the 3800 and the stock Fiero. The engine mounts will need to be custom made or you can buy them from several vendors. The 3800 swap has been heavily documented on this forum. Use the archives. A;l the steps and parts are listed and easily found.. Good luck on the project.
------------------ " 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 12-11-2025).]
Use Ryan at Sinister Performance (gmtuners.com) for you computer work.
Dennis has a point, the 4T65E transmission works very well with the 3800 and will save you a ton of money. If you want a manual later when money is better, do it then.
Question - was the 3800 harness from an NA or Supercharged swap?
Another point, the gage issue is already taken care of with your salvaged harness.
Hi there and welcome. I use a Getrag 5-speed in my car and it's not broken yet! No, seriously the Getrag is OK if you put racing grade oil like Motul 300 gear 75W90. One thing you will need is to upgrade the gearbox (transmission) mounts. The stock ones will just tear apart with the torque (especially the forward one). If you have some fab skills then a pair of TH400 poly mounts will provide the strength needed. Just copy the design to some extent of the original mounts, but with thicker steel and using the TH400 poly blocks instead of the rubber. As others have said, Ryan (Darth Fiero) of GM tuners is the one stop PCM programmer (at a very reasonable price).
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
Hi there and welcome. I use a Getrag 5-speed in my car and it's not broken yet! No, seriously the Getrag is OK if you put racing grade oil like Motul 300 gear 75W90. One thing you will need is to upgrade the gearbox (transmission) mounts. The stock ones will just tear apart with the torque (especially the forward one). If you have some fab skills then a pair of TH400 poly mounts will provide the strength needed. Just copy the design to some extent of the original mounts, but with thicker steel and using the TH400 poly blocks instead of the rubber. As others have said, Ryan (Darth Fiero) of GM tuners is the one stop PCM programmer (at a very reasonable price).
Ok, good to hear! I already have the transmission, axles, clutch cylinders, mounts, cables, etc. lined up for purchase (getting a really good deal) And thanks for the info on the front mount. Ill check out Darth Fiero! Just need to find the pedals, flywheel, and shift assembly.
------------------ Thanks! Nathan Shade "The Cheese Wedge" Yellow 86 GT 2.8 auto with a blue roof.
Use Ryan at Sinister Performance (gmtuners.com) for you computer work.
Dennis has a point, the 4T65E transmission works very well with the 3800 and will save you a ton of money. If you want a manual later when money is better, do it then.
Question - was the 3800 harness from an NA or Supercharged swap?
Another point, the gage issue is already taken care of with your salvaged harness.
Will check Ryan out! I have a purchase set up already for mostly everything for the manual swap already. (The guy who sold me the car had a manual parts car) Don’t plan on beating on the transmission too much.
The harness was from a turbo setup. L67 block and heads with l36 intake manifolds. ( the l67 fuel injector ports were filled in with rtv). Should still work for me? Hopefully?
Also, thanks for the advice on west coast. I honestly couldn’t buy anything from them anyway… too expensive.
Will check Ryan out! I have a purchase set up already for mostly everything for the manual swap already. (The guy who sold me the car had a manual parts car) Don’t plan on beating on the transmission too much.
The harness was from a turbo setup. L67 block and heads with l36 intake manifolds. ( the l67 fuel injector ports were filled in with rtv). Should still work for me? Hopefully?
Also, thanks for the advice on west coast. I honestly couldn’t buy anything from them anyway… too expensive.
That only difference between the 3800SC and 3800SA harness is only 1 wire for the supercharger bypass valve. I used a N/A harness and just operated the bypass valve on engine vacuum. Works fine on SC but on N/A you just don't use that one wire. If you already have the GETRAG you can certainly use it provided its in good shape and not abused.. However it will cost more $$$ for the clutch, cables and flywheel. There are mixed opinions here about West Coast Fiero mainly for taking too long to deliver parts. I've had good luck with them ( as I order in the off season) but others haven't. If you deal with them just check around to see how they are doing these days. A while back I did a swap for a guy that waited 4 months for delivery of his headers but they did finally deliver.
------------------ " 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 12-12-2025).]
Did you happen to grab the computer for the 3800 when you got the harness?
You may need to modify the harness for proper speedometer function.
That is correct. The VSS signal must be fed into a simple RC buffer circuit to provide the right data to the PCM and speedometer. A simple circuit in the swap harness will do it
------------------ " 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 "
That is correct. The VSS signal must be fed into a simple RC buffer circuit to provide the right data to the PCM and speedometer. A simple circuit in the swap harness will do it
Thanks for the info, does anybody have a schematic for the rc buffer? (Can make it myself)
That is correct. The VSS signal must be fed into a simple RC buffer circuit to provide the right data to the PCM and speedometer. A simple circuit in the swap harness will do it
His swap harness probably already has the circuit installed. He will have to change the plug for the VSS on the Getrag.
i never know which engine people are talking about when they say 3800.my 1989 buick engine says 3800.it would be better if people said '1996 3800' or whatever year.
i never know which engine people are talking about when they say 3800.my 1989 buick engine says 3800.it would be better if people said '1996 3800' or whatever year.
In this thread Ill be referring to the 3800 series 2 from 95-04 for the most part. Will be putting the aluminum intake from the series 3 and an l67 TB on it. (Dislike the plastic one, made the same conversion on my Buick) I am currently waiting for another car of mine to sell then will be purchasing my engine!
On a side note, ZZ Performance makes high velocity intake baffles that will improve the flow of the 3800 N/A manifold (30+ horsepower gain). They also sell high lift rockers or performance cams for even more horsepower.
------------------ " 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 12-12-2025).]
Definitely use Ryan at sinister for the ecu programming! Got both of mine from him and have 2 great running swaps. I got my flywheels from fierorog, his numbers on here somewhere. He has brackets for it all too. Definitely a worthwhile swap
On a side note, ZZ Performance makes high velocity intake baffles that will improve the flow of the 3800 N/A manifold (30+ horsepower gain). They also sell high lift rockers or performance cams for even more horsepower.
If only the intake would be in stock , def considering grabbing those 1.9 rockers though.
Definitely use Ryan at sinister for the ecu programming! Got both of mine from him and have 2 great running swaps. I got my flywheels from fierorog, his numbers on here somewhere. He has brackets for it all too. Definitely a worthwhile swap
shem
Ive sent fierorog an email about that flywheel! Will contact Ryan soon
, def considering grabbing those 1.9 rockers though. 
