How simple would it be to swap the 2.8L V6 mated with the 5-speed into a Fiero originally equipped with the 2.5L? I understand that I would need to bring the engine harness, gauges, and probably the PCM. I don't think I should encounter mounting issues, even though I'm swapping an 86 engine into an 85 frame.

why don't you just swap in a 3.4 and get some more power since your swapping anyways. But it will fit

id go with the 3.4 its better all around. better oil system and somethng with the heads having better coolant flow along with air
i like the 3.4 a whole lot better than that of any 2.8. go with the ecm upgrade too. while everthing is out.
i made the mistake of not spending the extra 300 bucks for a 3.4 and am regretting it deeply.
its definitely my next swap for sure.
best of all they fit right in with practically no mod at all
ps: the pushrod 3.4 is what im talking about... not the TDC motor thats a whole new story

[This message has been edited by BlackGT Codde (edited 12-09-2008).]

Because I found an 86 GT for cheap enough to get and replace my front drivers side suspension that got damaged when I got T-boned in my 85 SE. The main reason I'd do the 2.8 is because I don't have the 3.4, and don't really have the money to get it at the moment.

You will need to swap out the fuel pump to the higher pressure V6 one. If the Duke one is already a stick shift it's not too bad a swap. If you're going from auto to stick it becomes more difficult. If the you are going from a Duke/Izuzu 5 speed combination to the V6 getrag 5 speed then you need to swap out the shifter cables also.
If the GT cradle and suspension is any good you could move it all to the SE and have the WS6 suspension too boot

quote Originally posted by 2farnorth: You will need to swap out the fuel pump to the higher pressure V6 one. If the Duke one is already a stick shift it's not too bad a swap. If you're going from auto to stick it becomes more difficult. If the you are going from a Duke/Izuzu 5 speed combination to the V6 getrag 5 speed then you need to swap out the shifter cables also. If the GT cradle and suspension is any good you could move it all to the SE and have the WS6 suspension too boot

This has been the most helpful post so far. It is from the Duke/Isuzu 5 speed to the V6 getrag 5 speed. I'm guessing when I put in the wiring for the secondary dash pod above my center console I'll have the shifter cables exposed for easy access. As for the suspension, I thought regardless of engine type they all had the same suspension, but I'm guessing due to engine weights the rear suspension is probably somewhat different. What are the main differences between the Duke suspension and the V6 suspension?

I cant help you with the suspension question, but I bought a V6 car a couple years ago to do this to my 2.5 car. Some things I learned were that the radiator and coolant tubes are the same. Since its a manual-manual swap, no trans cooling lines to mess with. The whole center console and skeleton comes out to do the shifter cables, so I would clean that area up nicely when you are there. I believe the throttle cable will have to be swapped, again when the center console is out. It would definitely help to get a donor V6 car to snatch all the parts from as you come across them. I have a bunch of parts I took off of mine that I am not using, so if you need something specific let me know and I will see if I saved it.

-Joe

Edit to add: you will need the fuel lines from the tank to the engine, the ac hoses from the firewall to the compressor, and the dogbone from the V6 car amongst other things.

[This message has been edited by joesfiero (edited 12-09-2008).]

I live not too far south of you. I'll take your 2.5 when you're done with it!
Let me know what you want for it.

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Spent my days with a woman unkind Smoked my stuff and drank all my wine...

Never did this conversion but check the way the Duke powertrain was mounted and compare it to the V6 mounts. You will need the complete V6 wiring harness and I believe that you will also need to do a small amount of rewiring.

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87GT - 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite.
87GT - 3.4L Turbocharged engine, modified TH125H
" I'M ON THE LOOSE WITHOUT THE JUICE "

I just completed the swap with an engine from an 86GT/4speed into an 87 Coupe 5 speed Isuzu and have the car on the road. Here are the basics as I best remember:

I retained the springs from the 2.5 with no issues. The GT I believe has higher rate springs as it has the sport suspension. Here are the items to address:
• You need the fuel pump from a 2.8L
• The left side for/aft coolant tube on the 2.5 is about 6” longer on the 2.5. You can cut it down, but remember to double clamp it. I changed to the 2.8 coolant tube because I had one. It is a lot of work to change it.
• The for/aft heater pipe that connects to the thermostat housing through a molded hose is different for the 2.8. I changed mine, but you don’t have to…just use more heater hose.
• I believe the fuel lines are different; I did not check as I bought new ones from the Fiero store
• You need the dogbone from a 2.8…it is shorter
• You need an air filter. The rubber boot that goes from the throttle body to the 2.8 air filter will not clear the cables to the Isuzu box. I ended up cutting the stock boot about 4” from the throttle body and found a flexible one from a junkyard. It fit perfectly over the exit from the air filter and fit over the shortened stock boot after I ground off the ribs. Sorry, I do not know what car it was from. I wondered around the junkyard and bought 8-10 boots, and one of them fit.
• You need to change the throttle cable
• You need the engine harness from the 2.8+ECM+ECM mounting bracket
• I swapped in the engine bay cooling blower, and the rear wiring harness to power the blower. I do not know how important it is…the blower cools the distributor and alternator.
• The 2.8 harness plugged in to the 2.5 harness and all worked with no issues
• The motor mount is the same, but I put in a new one.
• I replaced all engine seals, the timing chain (the engine had 90K on it), the water pump and had the injectors cleaned.
• I think the AC brackets are different; my coupe did not have AC, but I swapped it in from my parts car.
• I used the alternator from the 2.8
• I installed a new Fiero Store HD RAM clutch for the 2.8 with the Isuzu throwout bearing
Hope I did not forget anything.
Jim

when you changed the wiring harness from the v-6, what part of the harness did you change?
just the part that was on the motor?
thanks, I'm doing this swap right now.
john

You must use the complete engine harness from the V6. This is the one you unplug from inside the car (connectors to ECM, connectors to main wiring harness). The other end connects to all of the engine sensors, injectors, etc. on the engine. You push this harness through the hole in the firewall and leave it with the engine. I also changed the rear harness so I had wires to connect to the cooling blower and cruise control. It is not necessary to change this harness, but you would have to supply power to the cooling blower. This harness begins aft of the battery (the back or wall side of the connector), passes over the frame rail into the fender well, and wraps around the back of the car behind the taillights. It supplies power to the trunk mounted cooling blower on the V6, taillights, backup lights, trunk light, and cruise.

I hope I answered your question.

Jim

thanks, one last question, you did not have to change the wiring harness from the ECU forward, correct?
in other words, the key, the heater wiring, etc.

Correct. I did not have to change the forward harness.

FYI, I found at least four variants of the forward harness

Auto/Stick...the wiring is different for the wiring for starter lockout: auto is on the transmission/stick is on the clutch pedal.
AC/Non AC: heater/AC control connectors are different.
Jim

quote Originally posted by bowrapennocks: • I believe the fuel lines are different. • You need an air filter. The rubber boot that goes from the throttle body to the 2.8 air filter will not clear the cables to the Isuzu box.

True for the 84/85/86. In 87 and 88 the 2.5 fuel lines on the chassis are compatible with the 2.8 V6 engine fuel lines and become plug n play.

The stock isuzu cables will clear the stock rubber 2.8 air intake tube. I prefer to go over, but have also seen others go under. It is a snug fit, but it works.

Thanks for the picture of the intake. I will go back and look at mine again. I have a spare, uncut boot.
Jim