Fiero advice needed

[mongo]

OK... here's the deal: I have a running and driving Fiero. My plan started out with a simple engine rebuild and spiraled from there into a Hybrid build with a 4T60 to replace the TH125. Everything was going OK until I drove the Fiero the other day (my son usually drives it). The drive train is in bad shape and getting worse every day. I have no time left to do everything I need to do to make the hybrid swap happen. I am thinking I just need to grab a complete running 3400 engine, tranny, and wiring to get the reliability and performance I am looking for in the time I have left before the current engine shoots craps.

Is anyone on this forum familiar with the pitfalls I am going to run into? Under my old plan there were TONS of problems to overcome but I did my research and knew what they all were and had plans in place. With my new plan, I am not completely sure what I am getting into but I am certain it will take less time than my old plan....

[mongo]

Looks like the only problems I am going to run into are the tranny mounts, axle length, shifter cable bracket, and that none of my original gauges will work with the new computer.

Damn! I just missed a complete engine,tranny,wiring harness with 40K on it for $400. I am on the hunt for another one....

[RedBird]

don't bother with a new computer and eveyrthing. as long as it's a v6 fiero, the 3400 will be close to a direct drop in. just find another 3 speed if yours is bad.

[asylummotorsports]

Well I have to throw in my 2 cents.

What's wrong with staying with the 3t40? They are plenty strong enough, lighter than a 4t and it would save you a bunch of headaches.

[Joseph Upson]

Well I have to throw in my 2 cents.

What's wrong with staying with the 3t40? They are plenty strong enough, lighter than a 4t and it would save you a bunch of headaches.

If you're going to go through the trouble of a tranny swap, you may as well reap the full benefit of the overdrive. 4 speeds are swapped in fairly easily and usually the mount problem can be solved by finding a 4 speed car in the right year range which will have the correct mounts for a direct fit. The guys on the Fiero forum can sort out the axle problem which is not difficult to solve. There is a link in my 6 spd thread on the Fiero forum to a downloadable file with specs across several 100 cv axles to find the correct inboard joint combo for what I believe is the driver side that may need a spline change.

It's been a while since I did the swap but putting the tranny in the car was no trouble at all.

I believe he is speaking of the assembly swap with PCM because it would offer more reliability by eliminating a tuning process. Dakota digital can take care of the odometer signal if an appropriate earlier speedometer gear can not be installed in the tranny.

Although I have done it with a turbo, I would highly advise against putting iron heads on the 3400 to keep the current ECM if any thoughts are leaning that way. If tuning is not an issue, the 730 ECM can be used to keep computer requirements a little less complicated. The Beretta 3.1 code would be a good base to start with.

The complete swap would be best and least time consuming since no tuning should be necessary.


The four speed auto is worth its trouble in MPG gained. The 3 speed runs over 3K rpm on the interstate

[mongo]

You hit the nail on the head! The TH125 is a rock solid transmission but I pull 3500 rpm at 75 MPH and only get about 20 MPG. Since this is a Fiero, in order to swap the motor I have to drop the entire engine cradle. While I am that deep in, I might as well do EVERYTHING in my power to make sure I get the maximum return for my efforts.

I have a second cradle to aid in the swap. I plan on getting my second drive train completely mounted (engine, trans, exhaust, struts, ect.) and ready to install to minimize my down time as an engine only replacement has been know to be VERY time consuming.

Here is how this all started: First I grabbed a 95 3.4 which came with a free set of 02 GA heads. So I decide to go ahead and build this as a hybrid. This caused me to need a new upper Intake and fuel system, so I needed a new PCM. Now I didn't really mind that since I also planned on putting in a 4t60 (which I also still need to rebuild) while I had it all apart. The trans was almost a direct swap and the 7730 solved my problem with the TCC lockout solenoid. So I got all of my machine work done on the block, collected a pile of parts, got ready to do the build and the car started falling apart at an accelerated rate. It was at this point that I decided that I would get 95% of the performance I was looking for with only 50% of the time needed if I just picked up a complete assembly out of a donor car. No matter which way I went, I still needed to do some custom wiring harness work and custom exhaust but I no longer have to worry about build time and the hassles with the PCM and programming.... I just made this all too complicated for myself because I love the hobby aspect of it all but I need to put that aside for now and be practical.

[Joseph Upson]

You hit the nail on the head! The TH125 is a rock solid transmission but I pull 3500 rpm at 75 MPH and only get about 20 MPG. Since this is a Fiero, in order to swap the motor I have to drop the entire engine cradle. While I am that deep in, I might as well do EVERYTHING in my power to make sure I get the maximum return for my efforts.

I have a second cradle to aid in the swap. I plan on getting my second drive train completely mounted (engine, trans, exhaust, struts, ect.) and ready to install to minimize my down time as an engine only replacement has been know to be VERY time consuming.

Here is how this all started: First I grabbed a 95 3.4 which came with a free set of 02 GA heads. So I decide to go ahead and build this as a hybrid. This caused me to need a new upper Intake and fuel system, so I needed a new PCM. Now I didn't really mind that since I also planned on putting in a 4t60 (which I also still need to rebuild) while I had it all apart. The trans was almost a direct swap and the 7730 solved my problem with the TCC lockout solenoid. So I got all of my machine work done on the block, collected a pile of parts, got ready to do the build and the car started falling apart at an accelerated rate. It was at this point that I decided that I would get 95% of the performance I was looking for with only 50% of the time needed if I just picked up a complete assembly out of a donor car. No matter which way I went, I still needed to do some custom wiring harness work and custom exhaust but I no longer have to worry about build time and the hassles with the PCM and programming.... I just made this all too complicated for myself because I love the hobby aspect of it all but I need to put that aside for now and be practical.

If by 3.4L you mean rear wheel drive block, I hope that you are planning to take advantage of higher compression since you are building it. I would certainly plan on at least 10.5:1 and a camshaft regrind or performance replacement. Those are small mods with big returns. You should also plan your tranny gearing well as you will have wide range to choose from with a 4 speed. if you perform the above mods I would aim for either a 3.33 final drive and stock stall converter or a 3.06 and slightly increased stall converter.

None of that is extra work because you will already be going through those parts. The stock Fiero automatic could not spin the tires from a dead stop. My 3400 with iron heads on it and 3400 pistons could do it bolted to a 4 speed could do it easily. Mind you it had a 2700 stall converter from the turbo pontiac sunbird and 3.33 gears.

I built my setup on an extra cradle first but found it was better to wire the engine after it was installed for a cleaner harness. If you go turbo especially since you are already using a 730 ecm, you can go with a 2.84 final drive and have plenty of power when you need it and excellent fuel economy when you don't. The 3800 SC is getting better than 30 mpg in some Fiero swaps. If you bump up your compression and stick with the stock cam or a conservative upgrade you should be well into the 30 mpg range. I managed nearly 28 mpg with a four speed manual running about 3100 rpm on the interstate and that was with a low compression 3100 which had iron heads on it with a turbo.

I know you're in crunch mode, but it's best to bite the bullet and build it the way you want it the first time.

[Ray Hamilton]

Go here http://www.fiero.nl/cgi-bin/main.cgi...i-bin/main.cgi with your questions.

[Ray Hamilton]

How can you get more compression from a hybrid 3.1(2.8 with 3.1 crank and pistons), say 10 or 10.5? Does anyone make pistons?

[Joseph Upson]

How can you get more compression from a hybrid 3.1(2.8 with 3.1 crank and pistons), say 10 or 10.5? Does anyone make pistons?

The store offers thinner than stock headgaskets. A combination of iron head pistons and gaskets would offer more range of variance also.

This is the best forum for anyone performing a swap with an aluminum head engine or variation of one for several reasons and that's why the inquiries from Fiero owners are increasing. Pennock's members are stuck on iron head motors and the few that have performed aluminum head engine swaps are not easy to get in touch with or not very helpful at times, with responses like "try the search button". It does have its benefits when it comes to ECM swaps for management of a newer/different engine otherwise in my oppinion this is the best place as it focuses on the engine itself not so much the car. This forum is also much better organized in a specific sense regarding topic sections instead of a technical section with everything grouped under that single heading.

[Superdave]

Ben has a OBD1 chip that was tuned for a 3400 in a Fiero, I'm sure he could make the changes needed to get it to run well with an auto trans. That would need a '7730 ecm and an engine harness from a cavalier or beretta.

[mongo]

Looks like I may have bought a little more time with the current Fiero motor. Those 2.8's really don't like to be run with only 5 of the plug wires hooked up solidly.

After all of the exchanges I have had on here.... I am leaning towards going back to the Hybrid and 4 speed auto and the 7730 ecm....

[60dgrzbelow0]

Here are some Fiero Engine Pull (Cadillac Engine Swap-In) images and "How-To" motor mount fabrication on the TOC that is data to add to what is available elsewhere on our forum:

http://www.thingsthatgo.ca/projects/v8fiero/fiero_out.htm