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fiero 2.5 to 2.5 swap

11K views 27 replies 7 participants last post by  ChevyTruckGuy 
#1 ·
i have a 85 2m4 fiero. it all the sudden started running really poorly. i checked the compression after going through the fuel system and ignition system and there was almost none. so i decided to just put another 2.5.

My question is does it matter what other 2.5 liter i put in it. like will an 88' 2.5 out of a s-10 work with all the rest of the original setup.

Any feedback would be great. Thanks!
 
#2 ·
no, a 2.5L is not a direct bolt in, but you can make it work. You need to modify the fierro head to bolt to the s10 block, and you need to keep the fierro head to run the fierro intake. you can keep the s10 head and intake if you wish, it should all pulg up fine but the throttle cable needs to be flipped i think- that's about it.

yes I knwo way too much about those 2.5L's. If you want to hot rod one i have a lot of build adcive that can build you a VERY nice 2.5L. Still under 200 hp (all the factory casting heads are somewhat restrictive), but a blast to drive and sounds mean as hell.
 
#5 ·
89 grand am

thanks for all the feedback. i was just using the s-10 as an exaple. i found a 2.5 for the fiero. it would be out of a 89 grand am. what would i have to do to make this one work with my 85' fiero.

...or would i be better off finding the same year 2.5 or putting in a 2.8. i found a web site that sends you everything you'd need to swap in 2.8 in place of a 2.5. any ideas... Thanks
 
#7 ·
Wait... everybody hold on.

You can't mix RWD and FWD. The Fiero (being a transverse engine) uses the FWD type architecture, so for the sake of this discussion its FWD.

RWD blocks, heads, and intakes are different. The starter is in a completely different place, the heads are different, and in general its just a whole different critter. Internally they are the same, but externally they are different.

So, skip the camaro and S10 ideas. Stick with FWD donors.

.... or go with one of the common aftermarket options, like the Northstar, SBC, or LS1 options.
 
#8 ·
curtis73 said:
So, skip the camaro
The 3.4 uses the same bolt pattern, its a common upgrade if your just looking for a little more power than the 2.8 unless you get a good deal on a used 2.8 the 3.4 would be a better choice as its almost exactly the same amount of work and a better engine.

A quad 4 out of a grand am is also a nice swap, if I was going to do it I would also swap the tranny out of the donor car as well. Better gears and you will probably get better gas mileage.

If you want a good jump in HP look at the 3800 SC or go NA and put a turbo on it. I would also use the tranny out of the donor car.

If you have lots of money and time you can order an adapter plate and install a SBC
There are several out there, I got mine from V8Archie (Google is your friend)
 

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#12 ·
curtis73 said:
It is the same tranny mount pattern... but the starter is in a completely different location, and the intake and exhaust manifolds are different as well as the heads.
You have to drill for the starter, you can buy a jig or make one. You also have to use the Fiero intake and exhaust anyway. The Camaro intake wont work due to the distributer. Other than some reinforcement webbing on the 3.4 and the starter holes its identical to the 2.8 from the outside.

tkas4x4 sounds like you need to find another Fiero Duke between the years 85 - 87
 
#14 ·
i'm not sure if i need a whole new moter or what. its runs but only 2000 rpm. it sounds like its running on two cyl. and is being flooded with gas. it blows out black smoke out of the exahust and backfires so bad that the dipstick shoots out 15 feet. we changed the coil, roter, distributer, plug, plug wires, egr, idel air control. what else could it be other than a hole in the piston? are these 2.5Ls bad for blowing up?
 
#16 ·
No, we also ajusted the timeing. The car was running great one morning then all the sudden going down the highway there was no power and i couldn't get it over 30 mph if i wanted to. would it be the cam or a hole in the piston. either way i think i'm going to need to pull the motor.
 
#17 ·
does it rev when its in park? If so it sounds like an ignition problem. The wiped cam and piston are both things that are easy to check for. Run a compresion check and pull your valve cover and check the movement of the pushrods with a mic. They will be a hair off from stock, but should be pretty close to stock, and each other.
 
#19 ·
tkas4x4 said:
i'm not sure if i need a whole new moter or what. its runs but only 2000 rpm. it sounds like its running on two cyl. and is being flooded with gas. it blows out black smoke out of the exahust and backfires so bad that the dipstick shoots out 15 feet. we changed the coil, roter, distributer, plug, plug wires, egr, idel air control. what else could it be other than a hole in the piston? are these 2.5Ls bad for blowing up?
http://www.fieros.de/en/articles/ignition.html

Ignition module also causes those issues. $15 at most parts stores.
 
#21 ·
tkas4x4 said:
it doesn't revin park. it wont idel. when it runs it runs really rough. there was no compression so...

You don't think there's compresion, or you took a gauge and measured the compression from each cylinder after you warmed the engine up?

Ignition can cause it to run really rough. A wiped cam lobe will usually still have some compression and in many cases will have greater compression than stock.

What were your readings on each cylinder? That can give us a big clue. There's no sense in just throing a JY engine in there when it may not be the engine itself.

Also, would it be possible for you to take a picture of the plugs and post it on here.
 
#25 ·
what is the cheapest way to rebuild this motor. i already suck 1500$ into this car, then it breaks. now i see the rebuild kit is 400$. if i was to sell it running good, i would probabley get 1300$ out of it so i dont know to do with it anymore. this thing was a money trap!!! do i cut my loses and sell it broke for like 300$, stick more money into it and dig deeper into this hole.
 
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