I have an 87 Fiero GT with approx. 63K original miles. I broke the flex plate while accelerating, and because their was a lot of oil leaks and such, I decided to have some fun just going through the engine while I have it out trying to create some extra HP.
So far I bored the engine .030 over, seriously ported and polished the heads (Stage 3), 5 angle valve job, port matched the intake manifold, put in 10 to 1 compression pistons, a Comp Cams 260H cam with 1.52:1 roller rockers. Sprint manifolds and 2" stainless Ocelot exhaust.
I will be adding a stall speed torque converter and have installed a shift kit in my THM 125 transmission.
I am wondering what amt. of HP I can expect from this combination, what stall speed will work best for this engine. Also, whether the injectors and/ or the computer need attention to make everything else work well together.
I would appreciate any constructive input.

170 hp

You can gain a little more hp by converting to the 7730 ECM. Easier done with the engine out so you can cleanly build/purchase the wiring harness and route it to make it a clean install. At the same time you could also convert to the DIS ignition system. Engine response would be much better with the 7730 ECM as compared to the stock Fiero setup.

To determine your injector size, you would need to know what the hp would be. Use the stock Fiero fuel pressure regulator at 43.5 psi. It's capable of supplying enough fuel since it's the same regulator used on the 3.4 pushrod which was rated at 160 hp. Injector flow rate is determined by the number of cylinders and the hp produced. At the suggested 170 hp, 17# injectors would be in order. Here's a calculator from www.fuelinjectorconnection.com

http://www.fuelinjectorconn...alculator/index.html

[This message has been edited by fierofool (edited 12-25-2014).]

You need to remove the intake neck restriction and the Y pipe restriction. Another member's 2.8 (La Fiera) has made 17X rwhp with a custom intake and a big cam and better exhaust.
For the intake search for the DAWG mod.

Even tho the engine put out "140" hp by the time it hit the wheels, our cars were putting out 115hp.

As far as how much HP you can expect, it's hard to determine but don't try to make the 2.8L become a 3.8L. In other words, don't spend a bunch of money of the engine because the gains aren't much. A fully decked out 2.8L isn't going to be much more than a stock 3.4L from a 93-95 camero/firebird.

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Every fiero has a story, It's our job to keep that story alive.

quote Originally posted by zzzhuh: A fully decked out 2.8L isn't going to be much more than a stock 3.4L from a 93-95 camero/firebird.

It'll be a fair bit more than that, but it will be quite expensive to do.

2.8 = boat anchor

The most constructive advice I can give you is to swap in a 3.4 if you like the look of the 2.8. 37 more cubic inches is a lot when you are talking small displacement engines.

I would not spend a dime on a 2.8 with problems.

Porting and polishing the heads and a hot cam will give you nothing without opening up the upper plenum and the exhaust manifolds and crossover pipe.

Everything said above and..............You can use most of the stuff you've bought in a 3.4 block. Cam and everything is the same. Heads are the same and you can use the exhaust and all the intake and fuel supply system. I don't think your pistons and rings will work since you are somewhere around a 3.1 with a 30 over bore.

Just havin fun, several of the modifications you've made seem reasonably conservative to me, and similar to those I've made for my 1986 Fiero GT.

My guess is those modifications presumably could pick up maybe an additional 10 to 15 horsepower for your 2.8L engine, but not yet as much as the additional 30 or so horsepower required to get your 2.8L up into the 170HP range.

For that reason, and employing much the same reasoning as fierofool --- but a lower HP input than his --- I recommend currently sticking with 15-pound injectors, the same size as that employed on a stock or nearly-stock 2.8L --- rather than switching to 17-pound or larger injectors at this time.

Another thing to consider is employing what is often referred to on this forum as a "DAWG modification" to enhance airflow through the fairly restrictive neck of a stock Fiero V6 engine's intake manifold.

Those comments aside, boring the engine 0.030" over (which apparently often sounds sophisticated to many people) usually can be prudent to help "clean up" the cylinders of a worn engine, but will not add significantly to the HP the engine had when it was new --- and, in fact, it can't!

Why not?


If one does the math, one will see that that degree of overbore increases your 2.8L Fiero engine's displacement by only a trivial amount --- maybe to a total engine displacement of 2.9L from 2.8L --- if that.

Phrased perhaps less charitably, trivial changes in engine displacement made to what otherwise would be exactly the same engine typically result in trivial changes to that engine's HP, versus what it was when brand new.

The presumably more welcome news is that Sprint headers on a 2.8L V6 Fiero seem to last forever. Also, if later you want to transfer those same Sprint headers to a `93 to `95 pushrod 3.4L V6 "Camarobird" engine which you might intend to use to replace your 2.8L Fiero's engine, you can do that easily with the same Sprint headers your particular 2.8L Fiero's engine already has, similar to what I did with my daily driver `86 GT on New Year's Eve of 2006.

The reason for being able to do that actually is quite simple, albeit likely not yet known universally: The cylinder heads of a `93 to `95 "Camarobird" 3.4L V6 engine are IDENTICAL to those on a stock 2.8L Fiero V6 engine.


Good luck to you with your project, Just havin fun --- and after just your first post to it --- welcome to Pennock's Fiero Forum, "neighbor".

Welcome to the forum. You will not find a better or more comprehensive knowledge database. If there is an answer to a Fiero related question, it can be found either here or in the minds of its members.
And merry Christmas!

Thanks a bunch to all who shared your thoughts.
I think I have the gist of what I can expect realistically. Fuel and ECM are week links along with possibly the exhaust Y pipe. I was just hoping to wake it up a bit and make it a fun ride.

I totally agree with "use a 3.4 and Not the 2.8" . and if you are going to put more power in front of a 125 trans, putting in a higher stall and a shift kit, you better rebuild the trans while you are at it, it won't last. (better yet install a rebuilt 4t60 overdrive.)

Superior and TransGo are some of the better shift kits and they should be available for the 125 transmissions, but you might also want to put in some heavier duty clutches at the same time, especially if you go with a beefed up 3.4. New stock clutches would certainly be in order for your modded 2.8 even if the net hp gain is as small as indicted.

3800 SC!!!! I did mine for around $1200. Amazing power, and faster than you want to go.

Here a thread where they dyno'd 2.8, 2.9, 3.1, & 3.4 Fieros on the same dyno/same day. If the numbers are not high enough for you, cut your losses and do an engine swap.
https://www.fiero.nl/forum/A...130314-1-082335.html