The 2.5 Pontiac Fiero engine also know as the Iron Duke does not get a lot of respect. Dave Storlien decided to modify one anyways to see just how much naturally aspirated horsepower he could get out of one! Off the shelf parts (some modified) and a custom ground cam are all he used to significantly increase the Iron Dukes horsepower and torque output. Come along for some dyno testing fun and check out the results!
Link do Vídeo
So to help people out on the I thought I would post the flow numbers on the Vin A S10 cylinder head.
Box stock head flow Intake w 1.72 valve .100=46.3 cfm .200=89.9 cfm .300=111.2 cfm .400=121.3 cfm .500=127.2 cfm
Ported intake w 1.970 VW intake valve. .100= 63.9 cfm .200=127.8 cfm .300= 166.7 cfm .400=189.9 cfm .500= 192.1 cfm
Ex flow. w 1.625 Pipe .100=46.6 cfm .200= 86.3 cfm. .300= 125.3 cfm. .400= 145.3 cfm
Ported Ex .100= 65.9 cfm .200=112.1 cfm .300= 141.7 cfm .400= 156.6 cfm
2 of the head bolt holes in this head have to be elongated to fit on the Fiero block.
This engine had a 17 yr production run.
Found it's way into 19 different car models.
Has the same bore & stroke as the DZ & Boss 302.
Made the same power per cu in as everyone's stock V8s.
The only failure is people's understanding.
so its not an iron duke nor is it a 2.5 … good job. downvite
I bet theyll hit 280 with a turbo
These aren't built for that abuse had 1 in s10 had 4 years 400 hundred thousand miles but like said had replaced time gear
Aluminum,gets too hot
Port the intake in the 2 barrel carbureta for more air..
Alot of work for not that much hp tbh. My 8v 2.3 out of my volvo is pushing 170 hp. Original engine with only increased turbo pressure. 0.9 bars.
172HP on gas is good enough for me.
Dump the induction setup and go for atleast 2 Mikuni CV carbs, but 4 would be better
Why does everyone go with these weird downdraft carb intakes for 4 cylinders?
You'd be better off with 4 lawn mower carbs as far as fuel mixture goes.
With this you have to have the inside cylinders way too rich to let the outside cylinders get enough fuel.
Wow, wild to hear one of those at 5000! In the cars I worked on with this engine it seemed like valve float kept it below 3500. Maybe it just could not move anything through the head, dunno but they didn't seem to rev at all.
Carb and induction is killing the power
Just add a little boost and wa-la 200 easy
If anybody knows of a shop (like this shop) that is willing to work on fieros in the Ohio area please drop a line! In need of a tune and more boost! (88' formula 3.2l 60* making 220hp/260ftlb on 10lb of boost with an intercooled Garrett gt30-r)
I have an iron SD4 head with edelbrock intake I am replacing that would wake this bottom end up.
Let me know. Im rebuilding the 2.7L SD4 in one of my cars, and wont be using most of the top end. The casting number is: 1003223 the head is cut for 2.02 intake valves and 1.625 exhaust, it has been ported. I'll be flow testing it next week on a SF750.
Sounds just like my 84 Fiero at idle
I kind of want to see that go into a Camaro now lol
interesting
I need one of those intakes and one of those exhaust manifolds for my 87
We used the 437 aluminium head made 324 at 8100 that was injected on methanol crane track roller, jesel rockers etc. That was a 2.5 engine. Stanton head .Still got it, needs freashened up lol. We run the fontsna now 325 or so. Easy check my yt channel
can you please do this to my Fiero?
My 84 Fiero Iron Duke need those Upgrades Too ! 172 hp is good enough for me !
what kind of top speed can a stock 2.5 can go, my 86 2.5 and tack I redline at 73 mph I just got a tack filter will that help the right size tires are on it, I dont know what to do. other wise 65 mph is fine
Dave, I got this comment off of a forum – thought you may want to ponder it. Comment follows—>
Once upon a time I had a 87 Pontiac with that engine. Its timing gear disintegrated and since I was dirt poor I rebuilt the engine myself. My cost was only about $325 and it ran many miles afterwards. It was a fun project so I can kinda relate to this build.
As for the setup in this vid… the somewhat crude intake design I think it hurting the performance. The runners are not equal length and the suspended fuel has to go around sharp corners. I'm thinking that interrupts the laminar flow and makes for poor atomization as it reaches the intake valve. I say either go FI or make a intake with the carb sitting about 250-300mm higher and pipe the tubes to the bottom of the box.
Something I need to remind viewers about is that a Holley 2bbl carb is not rated at the same airflow depression as a 4bbl. The 4bbl is flowed at 20.3 In depression and the 2bbl is flow at 40.6 in depression So the actual CFM of a 500 2bb is only 353.3 CFM.
might be able to get more RPM out of it if you to at least get the .050 duration about 264 I would keep the valve lift about the same but if you are running the swirl port cylinder head I would put that baby back on the dyno and keep retarding the timing lower than 30° maybe try slowly work down from 30° down to maybe about 22° the way those chambers and swirl ports you don't need that much ignition timing due to being very efficient you might be able to pull a little more out of her I think that's why the engine is not revving up almost like you got the brakes on. The camshaft that's already in there you should at least get 5500 to about 6,000 RPM with that kind of stroke
The camshaft duration for that long stroke is a little small but the horsepower and torque will move that Pontiac Fiero down the highway excellent and it should last a very long time great numbers for an engine with only 5000 RPM
K swap it
David Vizard have ported a head for Richard Holdeners 2.2 Buick project.
I wonder if the Iron Duke heads are of similar design and something similiar could be done.
David has videos on it. Maybe worth checking out.
The stock air filter on a gm 2.5 L iron duke can be too restrictive at the max HP.
The engine really needs a larger surface Area filter if you explore boosting the HP.
With the Camaro here a Fram air filter was so restrictive you might get low acceleration and top speeds like internet dolts claim. A GM Ac filter is better and less restrictive.
Some brand new Fram filters i used would even collapse the air filter when they were a few months old. Then you have more HP since the dumb overly gooped up air filter was in place.
A clogged up cat converter also can limit the HP of the iron duke at higher rpms too.
The 88 iron duke had a balance shaft IIRC. Seems thats whats missing here?
Dammit Man
We need these guys to work their magic on an Iron Duke, in our 1950 Willys Jeepster
That thing is severely underpowered and vibrates like a box of rocks
No, but I had techs working for me, I guess I need to dig up the old TSBs dealing with these issues.
The 2.5 is one of the best kept secrets in the world of sleepers. It will take just about anything you can throw at it. I've seen a handful of them cranking out 300-350 horsepower with turbos or superchargers.
Pretty cool! It sounds good, nothing like the iron duke in my Indy Fiero.
Can u text me and help me do the same to my iron duke fiero
It was a typical 80's GM turd cracked blocks, busted head bolts, blown head gaskets, it's one of many reasons why GM went
from over 50% market share to the lower 20's it is in now, everybody went with the good Japanese stuff and will never come back!
Smokey Yunick took a 2.5L Iron Duke(1988 basically stock) and pulled 250hpand 267lbs from it. He modified the distributor a little and put a turbo blowing into a supercharger using a Holley 2 barrel carb for the fuel control. By keeping the air intake temp at 300F or better he avoided detonation running 93 octane gas. The engine was stock otherwise. GM really screwed up by not letting this engine run as well as it is capable of doing. I had 1988 S10 with that engine and a 5 speed trans and it just felt awful. It always felt like it wanted to run harder but just couldn't. After looking at what GM did to the engine I can see why it failed.
After some research & bouncing around ideas…I think reworking the Iron duke is the wrong approach…Rather, I would start out with the old non-crossflow head 3.0 marine version, (yes with the old SBC bellhousing pattern). At 9.3 CR would be a good starting point for the likes of centrifugal supercharging…the poor airflow at the ports negated by some, say 10 Lbs of boost. Yes, of course go full roller to help the valvetrain cope. The makers of industrial forklifts make a 4Brl intake for this engine…& of course a fabbed exhaust……Add in that Holley Sniper EFI to deal with dialing in procedures. Dunno, that's just the way I'd approach it.
I wonder if the Honda 2.0 k20 would fit in those Fiero s. My son has a rsx s type with a ebay turbo kit and it made 450 whp. Those k20s are bullet proof.
Why not add port injection (looks like the fuel rail is there) and distributorless ignition.
Or maybe have started with an '88 or newer Tech IV. They were improved. The '88s and newer have a balance shaft. Maybe that would quell the harmonic you mention.
The highest output Tech IV came with 110 hp stock.