DAVE'S FIERO

A comparison of the original 2.8l V6 and the 3.4l Dual Twin Cam V6:

These times were derived from the Car Test program.
These times were provided to me and I do not know
how accurate they are, I will post an actual quarter
mile time when the track opens.

If anyone is interested, here is the story of how I installed a 3.4l TDC Chevy V6 from a 1992 Lumina Z34 into my Medium Red 1988 Fiero GT with 5-speed Getrag transaxle. There are some photos (click on the hyperlinks) that were taken recently while the engine was removed awaiting a new clutch. Here are the details and my thoughts about this engine swap:

The only way I would want to do this swap is to get a running car, but as far as I remember you should only need engine, engine wiring harness, fuel lines and I also used the front motor mount and one of the rear suspension parts to fabricate an adjustable dog bone.

If you are considering this swap you should know that all 3.4TDC (Twin Dual Cam) owners need to inspect timing belts closely and the idler pullies! I am told that this engine is not an interference engine but I do not want to deal with a belt failure, and the idler pullies commonly are needed.  Replacement costs are approximately $100 for a new timing belt and idler pullies.

How this car and engine swap came to be. Actually my coming to acquire this was a process of elimination. I wanted to try a fast mid engined car.

1. German Cars, While I love German cars, the only affordable one is a 914 ( I hate air-cool) and a swap would need to be clean which left me with few options.
2. MR2, too expensive at the time, not to familiar with options for a swap and not what I found a deal on at the time.
3. X1/9 It is hard to find one that is not trashed and or not completely rusted out, I thought about swapping a VW GTI (rabbit) engine but looked like there would be a clearance problem, as suspension and water pump looked like they would need the same space and I thought I would need them both.
4. Fiero, I Happened across an 88GT Fiero at an auction yard, waited about 8 months for them to get papers in order to sell. At the time I bought the car I had no idea that there were so many improvements to the 88 model. Then through friends I was told of a Lumina Z34 which had been rolled and good body parts stripped but with a jump could be driven onto the trailer (some suspension damage). Although it did require a 12hr drive to get it, it was located in the middle of Montana.

SOME POINTS OF INTEREST IN THE SWAP:

Engine bay with fuel lines rerouted and fake dogbone

Right strut tower with dogbone mount removed

• ACCESSORIES are all Z34, except for the removal of the power steering pump. I removed the pump and used one of my old timing belt idler pulleys for the belt to run on. I threaded one of the PS mount holes and even used the bolt that comes with the new idler pulley.
• AIR CONDITIONING. I have modified the AC hose in order to use the new compressor but I am unsure of a plan to get the system to cycle properly (HI press switch on Fiero is on the compressor and it's in the lines on the Lumina) This is not a top priority now, but as long as I had to bring along the compressor (for the belts) it might as well work!
• COOLANT LINES were rerouted be using commercially available pieces of plumbing.
• CRUISE CONTROL. I am pretty sure I can (with the Lumina control and a little creative mounting) just plug in the cruise control actuator.
• ELECTRICAL
  • WIRING HARNESS was done buy spending about a week in front of the TV while tracing wires on the schematics of both cars till I knew which wires I needed and where to put them. Actually a lot of the colors matched up! The most difficult part of the swap by FAR was the electrical, I built a harness by myself but I have seen companies offering to build a harness for $350 (I think you have to send in a 3.4 harness and a Fiero harness?).
    I spent three days double and tripple checking the wiring worried about frying the computer, but when I was satisfied I hooked up the battery, cranked it for a bit to get oil press then pluged in the fuel pump relay and it ran and idled great!
    Still, I strongly recommend buying a harness per above, sorry I don't know the site, maybe you can find it through the Fiero Archies?
  • VSS SIGNAL: I chose to leave the Fiero's VSS hooked to the speedo and use the sensor for the Lumina and build an interrupter (I used a part out of a dead auto transmission and ended up cutting every other tooth off) which I mounted on the right tripoid joint, had to play with # of teeth, the engine won't run right with to few and too many causes the computer to shut down when it perceives 110 MPH. This also allowed me to fool the computer by approximately 75%, (if calculations are right it should shut down at approximately 150 MPH). I have only done 130 so far but ran out of road not power.
• EXHAUST 
  • EMISSIONS: Fortunately we are running smog tests tailpipe first (if you pass out the pipe you don't have to open the hood) and I am able to pass without the cat, though they do not like the supertraps (no probe hole).
  • MUFFLER: I am running supertraps 5" mostly because that is what I came across for a deal - $100 for a pair of used supertraps. Here is the only place where I am considering making some changes, I bought a cherry bomb type of muffler and cut a hole in the middle of it, welded a v spike in it to help with resonance and welded a down pipe directly from the Lumina manifold to the center hole, then I ran out both sides to the super traps.
  • My suggestion is just simply to run the down pipe directly to one side and use the 4" supertrap, this only gives one exhaust but no need for more and the 4" will fit better than the 5". The stainless Supertraps also have a shield that would allow the mufflers to be mounted a little more recessed.
• FUEL LINES: The fuel lines need to be rerouted for the 3.4 TDC motor. The places the lines in about the same location as the original 1984 Fiero's.
• INTAKE was simply using the Z34 intake boot, cutting the Fiero boot and slipping a little piece of 4" ABS in (local hardware store).
• MOUNTS:

  Adjustable dog bone mounted behind alternator cooling duct (pulled back for photo)

  Right decklid hinge modification

  • ENGINE & TRANSAXLE. As the block of the 2.8 is the same as the 3.4, the engine mount is stock. On the rear mount I slightly enlarged the holes where it bolts to the transmission to lower it a bit. By lowering the rear transmission mount it also brings the transmission snubber closer to its mount which helps. As the front trans mount was a weak point for the Fiero (My opinion) I fabricated some brackets so that I could use the Lumina front mount (no $).  I used one of the stock holes in the cradle and welded a piece of angle so I could use both studs.
  • DOG BONE: As far as the dog bone is concerned I again fabricated one that is adjustable using some threaded stock and the rubber isolators used on the Lumina rear suspension links (next to no $).  The best position I found for it was mounted low (below the alternator) there were some bolt holes in the block. I mounted the other end to directly to the sub-frame. 
  • FAKE DOG BONE: Mostly for cosmetic reasons I mounted a bracket to the firewall to allow me to mount a dog bone to the stock Lumina mount, I do not think the firewall is strong enough to do anything and I am watching for cracks, but as the other mounts are doing the work this allows me not to have it look like something is missing.
• FIERO CHASSIS MODS:
  • THE RIGHT DECK HINGE: must be cut for clearance (also loose one deck lid spring).
  • ORIGINAL DOG BONE BRACKET: The chassis side of the dog bone body mount was removed as it could not be used.
  • O2 SENSOR: A small dent was make in the trunk to give the O2 sensor a little more clearance.
  • DECK LID WEATHER STRIP: Originally the weather rubber seal on the front of the deck lid was was removed during the installation. I had to replace it, water was getting in the spark plug holes. Replacing the seal fixed this. (This seal is usually removed during one of GM's fire safety recalls, so I was lucky it was still there! )
  • NOSE MODIFICATIONS: I found a need for headlight modifications.  I would like to find a good looking way to vent the radiator out the top as I am sure this would help high speed handling as well as better speed) better to fix the problem (high pressure under the hood) not the symptom (headlights blowing open).
• COSTS: Here is where some people will cry foul, but I am telling the TRUTH! I purchased an 88 GT approximately 110K miles for $1,000 (with rod knock), then I ran across a rolled Lumina Z34 (auto) with 76K for $800. Used supertraps $100, Timing blets $100, Centerforce Duel Friction racing clutch $325, Misc items $100, I recovered approximately $200 from the auto transmission and the brake system from the Lumina.
• RESULTS: I can fool most people that do not know that 3.4's don't come in Fiero's to thinking it is a stock option.
• BRAKES:   While the 88 brakes are ~1inch larger and vented instead of solid like the 84-87 Fiero's, they still need improving on.  Most of this research was done by  Mr. Mazza of Web Electric Magazine which has a lot of good information, both Fiero and electronic.
          This upgrade uses stock calipers and pads.  The rotors are changed to increase the diameter over an inch to 11.5 inch rotors.  One very nice feature of this upgrade is that you can still use stock 15inch rims, but you will not be able to use 14 inch rims.  This upgrade also does not affect the
  track of the car either as it does not move the wheel in or out.
          The key ingredient is the rotors which have the correct offset and thickness.  They are off the rear of a 97 Firebird and can be bought at NAPA (Part # 4886407) for ~$25.00.   These are slightly different than the stock Fierbird rotors in that they are thicker at the mounting surface, which makes them better than the OEM
  Firebird rotors for this swap.  They do need to have drilled for the Fiero bolt pattern (5 X 100).  The hub centering hole is also larger than the Fiero's.  This may be a difficult part for some without access to a lathe.  You just need a collor that is the same inside diameter as the Fiero rotor and same outside diameter as the inside of the Fierbird rotor.
             Then you need to build a bracket to place the caliper out on the rotor. What I did was get some 3/16 steel plate and drilled four holes.  Two to bolt it to the hubs and two to bolt the calipers to.  These two need threads on them so I tack welded a nut on the back side.  I tack welded the nut on while the caliper was bolted on so that I knew that the nuts were in exactly the right spacing and straight.  These adapter brackets need to rotate the caliper  ~30 deg as the bolts will interfeer with each other if you don't.  I also went to a nut and bolt shop and bought grade 10.2 bolts as these are important.
            I hope to have a picture or two to add soon.  These rotors look huge behind
  the stock 15 inch wheels.
            I also hope to add an adjustable perportioning valve soon as the Fiero
  seems to have too much bias toward the front.  This upgrade also must be done on all four wheels as if you only do two as I did first (fronts), they will lock the fronts long before the rears are
  doing much of anything.
            Just so I have absolutely no liability concerns, this is just what I did and I do not suggest you do this to your car as brakes are a critical feature on cars and should not be modified unless you know what you are
  doing.
• Air intake:  I have grafted the right side fender vent from a Trans-Am over the stock air intake.  This is mostly for looks, but I think it adds a little ram-air and certainly does not hurt. 
  

As far as performance is concerned, the car is not blinding fast but very respectable (sorry no exact #s yet). I have not lost any drive ability. I am getting approximately 24 mpg and have gotten 30 mpg on a tank that was only freeway driving, but this is very right foot adjustable.  I consider retaining good mileage an important consideration as the 10 gal tank is small enough that I am sure most want to stretch it as far as possible.

I had no outside information other than the wiring schematics when I did the swap, I looked but found nothing. 

I did not do a good job of documenting the swap, just kind of jumped in and did it.

Please feel free to contact me if you have any other questions or info that might be helpfull on this site.

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