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1988 Pontiac Fiero swap by Firezappy
Started on: 07-01-2020 08:59 PM
Replies: 9 (670 views)
Last post by: theogre on 07-02-2020 02:53 PM
Firezappy
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Report this Post07-01-2020 08:59 PM Click Here to See the Profile for FirezappySend a Private Message to FirezappyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Hello, was trying to do some brainstorming on ideas. I have a 88 2.5 3 speed auto Fiero. I would enjoy some more power, but mainly less noise and smoothness. What 'good engines' bolts up to a THM-125? I was considering a series 1 3800 none turbo, just a bit more power. I would use a 2.8 but I feel like there is more reliable engine options out there. Almost considering to go with a carburetor and skip a large portion of wiring. Maybe I should be looking at a 305 instead? Or would a 3800 series 1 not have that many differences? Is there a method to limit power on the low end so as to not rip apart my transmission if I floor it?

I know a lot of people hate on the THM-125, but at least on the 88 it's third gear feels oddly high, it is great for cruising at 60 on the highway. Does not help acceleration of course, but the torque converter feels slippery enough to sort of make up for it. As far as 3 speeds go, it has been one of my favorites.

I am currently in the middle of replacing the transmission in my main car, a 1996 Chrysler New Yorker. It has a longitudinal engine that so happens to also be front wheel drive. Maybe that is wearing me out due to how there is no space for anything, but I just don't want to be making my own axles and linkage.
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Mike in Sydney
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Report this Post07-01-2020 10:16 PM Click Here to See the Profile for Mike in SydneySend a Private Message to Mike in SydneyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Easiest swap is the 3.4l from the '93-'95 Firebird and Camaro. Lot's of information around on that one. Here's a good reference: https://westcoastfiero.com/...gine-conversion-info

The 3.4's are getting scarce but you can get long and short block rebuilds from JEGS for around $1900 US. See this: https://www.jegs.com/i/ATK-...%28+3.4L+%2F+207+%29

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Firezappy
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Report this Post07-01-2020 10:56 PM Click Here to See the Profile for FirezappySend a Private Message to FirezappyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was snooping around and I don't see many post with the 3.4L engine with the 3 speed auto. I guess it should just bolt up, but what about controls? Main reason I brought up 305 is because Archie sets them up with that transmission frequently. The reason I brought up the 3800 series 1 is also because back in the 80s that combination was used with several cars, the 3 speed and 3800.

The 3.4 almost feels like uncharted territory, although maybe my searching skills are just weak. It would be really cool to change the transmission into a manual, but finding a donor car can be tough. I want it to look as factory as possible still, don't want a messed up looking inside.
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Notorio
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Report this Post07-02-2020 12:37 AM Click Here to See the Profile for NotorioSend a Private Message to NotorioEdit/Delete MessageReply w/QuoteDirect Link to This Post
As Mike has said the 3.4L swap is the easiest one and there are tons of threads on the Forum to show you exactly what to do.
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olejoedad
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Report this Post07-02-2020 09:06 AM Click Here to See the Profile for olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
A lot of 3.4 swaps are performed with the 4T60 four speed auto transmission. Great combo in a Fiero if the trans has 35/35 sprockets and the 3.33 final drive.
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fierofool
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Report this Post07-02-2020 09:30 AM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 3.4 is essentially the same block as the 2.8. It's a straight bolt-up to the TH125c Fiero transmission. Of course, you would need a Fiero V6 automatic ECM and engine bay wiring harness. Grabbing a blown engine from a U-Pull-It yard should give you everything you need for the swap if the Fiero Buzzards haven't cannibalized it.

That would take you from the 92 HP of the 2.5 up to about 160 HP. Keeping the converter on the exhaust system will give you relative quietness of the exhaust note and with the 3.4 being internally balanced, it's much quieter and smoother.

I have an article on the Georgia Fieros website that covers the 3.4 install. It's actually an upgrade from a 2.8 but it should give you some ideas.
http://www.gafiero.org/bbs/...56750cb&topic=2080.0
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qwikgta
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Report this Post07-02-2020 10:37 AM Click Here to See the Profile for qwikgtaSend a Private Message to qwikgtaEdit/Delete MessageReply w/QuoteDirect Link to This Post
My advice, fix your car, as is, and enjoy driving it. The questions you're asking are all over the place. You need to do a lot more research before you attempt an engine swap. Just fix it and enjoy it. You will be much more happy in the long run.

Rob
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cam-a-lot
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Report this Post07-02-2020 12:07 PM Click Here to See the Profile for cam-a-lotSend a Private Message to cam-a-lotEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by qwikgta:

My advice, fix your car, as is, and enjoy driving it. The questions you're asking are all over the place. You need to do a lot more research before you attempt an engine swap. Just fix it and enjoy it. You will be much more happy in the long run.

Rob



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sourmash
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Report this Post07-02-2020 12:25 PM Click Here to See the Profile for sourmashSend a Private Message to sourmashEdit/Delete MessageReply w/QuoteDirect Link to This Post
I concur.
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theogre
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Report this Post07-02-2020 02:53 PM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
Note:
Many Fieros have problems w/ gas pedal, the throttle cable, and/or TB/TBI...
Worn pedal parts, cable stretch, worn shaft in TB/TBI or all at once will hurt performance and some will hurt the "swap" too.
See my Cave, Throttle Cable
Search PFF for pedal problems. The big plastic "bearing" on the pedal rod wears and gets a lot of play. Worse if fools use oil/grease on it.

Many needs ECM scanner at some point...
Just read throttle % w/ pedal floored and many will see 70-85% max.

Or just have help to hold pedal down and look in the TB/TBI...
Then turn TB/TBI arm/"wheel" until you reach WOT and often see a big difference. The cable should pull the shaft very close or at the throttle max limit.

When you can't reach WOT... that can affect the auto trans too because of TV cable and ECM.
ECM may not release TCC and/or TV Cable may not "kick down" when needed to pass on a highway etc.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)


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