Modified Pontiac Fiero 2.5 Iron Duke (Dyno Testing!)

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!
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[@racerd9669]

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.

[@Toys4Life]

Useful info - thanks Dave!

[@lawrencebergman3093]

Get a pontiac sd4 cylinder head and a clifford or a 2bbl intake

[@buzzkill7349]

Very nice. What rods were used? Did you fill the block? I'd love to build one for one of my fieros. Great video!

[@racerd9669]

@@buzzkill7349 The Con rods are a speedmaster SBC rod that is 6.125 long to work w the compression hight of the Ford Windsor pistons. And no the block is not filled.

[@FieroWannaBe]

Those are pretty good numbers ported. Pretty much inline with what my Iron SD4 Head flows up to .400 lift, then the sd4 valve sizes start to work in its favor. what is the volume of the ports on the S10 head? both my SD4 heads are roughly near 180cc.

[@MidwestOptimist]

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.

[@Toys4Life]

Agreed, It was originally made to be a low revving torque engine, and it does that very well!!

[@Friedbrain11]

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.

[@Toys4Life]

Smokey did some cool things! Depends on what you define a failure, I think GM made this thing to be a utilitarian workhorse, and in that regard given all the mail trucks it's in and other vehicles throughout the years it may well have been quite profitable for GM, but that cylinder had really is like trying to breathe through a straw on a 2-mile run.

[@e34boat88]

is this the hot vapor engine?

[@brianluna2808]

Failed? Used in millions of cars and trucks and government postal llvs is hardly a failure.

[@mathuetax]

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.

[@Toys4Life]

It wasn't float - but there were vibration harmonics that were messing with the carb float causing issues.

[@the_car_guy5915]

​@@Toys4LifeThat's weird lol Do you have the same issues with the Holley 500 or was it factory specific carbs?

[@radioflitercairplanes1715]

I showed my great nephews thus video , they race there 355Z's here in CT at Lyme Rock race track..one of them is all hyped up and looking for a Fiero. Great video.

[@Toys4Life]

That's awesome, hope they enjoyed it and hope the find the right project Fiero!

[@AndieBlack13]

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.

[@Toys4Life]

Sounds like you put some thought into it, I like it.

[@racerd9669]

I do not think the NonXflow head would make much power, but none of the factory cast iron heads are much for air flow. I do have flow numbers on the head I will have to look them up and see what flow it did have. As far as roller cams, good luck finding any, and the factory roller cores are way to small to get anything large enough for this big of a 4 cylinder engine. But thanks for your input, that is what this is all about, making people think.

[@flathead1271]

Try Ultradyne!

[@chuckragsdale2904]

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.

[@Toys4Life]

There is something cool about taking a modest performance Duke engine and boosting the heck out of it!

[@racerd9669]

But think about this, if the duke had a SD head on it, it could make that power N/A. Only problem is the SD heads are impossible to find.

[@chuckragsdale2904]

@@racerd9669 yep... thanks to cast iron and gearhead ingenuity there's a lot of future horses sitting in some pedestrian looking Chevy Cobalts and mini-pickups.

[@racerd9669]

@@chuckragsdale2904 I agree 100%, plenty of interest in the old Iron Duke still today.

[@aaronmcilvain8077]

I think you are thinking about the Pontiac super duty.

[@70sport37]

Great ending !

[@Toys4Life]

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.

[@racerd9669]

I appreciate your input, so lets look at why the intake was designed the way it was first and then go into the draw backs. The intake was designed to work with all the Fiero factory linkage and air cleaner, so it was packaged to fit the Fiero engine bay. This build was done by myself and some interns working in my shop. It was never built to run a carb. it had a modified stock TB that was sleeved for a Buick V6 throttle blade and multi port Fuel injection. So wet flow was never a big consideration. Now if you look at the EGTs you will see the quirks of the carb on a FI intake. If you notice at the start of the pull the inboard cylinders have no fuel, hence low EGTs and the outboard cylinders are running at about 1050 EGTs and then the inboard cylinders catch up and their EGTs start to run about 1200deg. and all 4 cylinders are running very close, hence making equal power. Also the engine made best power with only 30degs of timing. I would say that is very efficient for the old antiquated duke. Even the the best GM could do with the 2001 Vortec headed SBC was 30degs of timing, and that was after 46 years of building that engine. I agree the intake could have been a better design, because it was built with 1 3/4 steel tubing. It really needs a 1deg taper angle to help velocity and remove restriction. But as far as wet flow I think you better look at the EGTs again. The engine is running on the long runners at idle and under low load, but as soon as you load the engine hard all the candles are lit and running very close together. I must admit I was surprised myself that the long runners were getting more fuel at idle and low load than the short runners.

[@RearEngineShop]

Pretty cool! It sounds good, nothing like the iron duke in my Indy Fiero.

[@Toys4Life]

Fun little car!

[@DucatiPaso750]

It doesn't look like this engine would fit in a Fiero anymore. At least not with the luggage compartment in place.

[@Toys4Life]

Fit is just an adjustment or two away...

[@racerd9669]

@@DucatiPaso750 It was run as it is in my 86 Fiero. That is the reason the Intake was built as it is.

[@DucatiPaso750]

@@racerd9669 I hope you are having fun with it. 👍

[@blanchae]

It's amazing how far engine design has come. My normally aspirated 2007 Jeep Compass 2.4L 4 cyl comes stock with 172 hp at 6000 rpm and 165 ftlb at 4400 rpm. I do wish there was more torque though.

[@Toys4Life]

Couldn't agree more!

[@jovanluit8262]

My 84 Fiero Iron Duke need those Upgrades Too ! 172 hp is good enough for me !

[@Toys4Life]

I hope I get to take it for a spin when Dave tosses this into his Fiero!

[@VladimirPutin-cz5zy]

I could imagine this in a 80's S10. Would be fun.

[@magnusdanielsson2749]

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.

[@Toys4Life]

I doubt it, but let's just a guess.

[@dj4monie]

The answer is to find and not pay too much for the Pontiac Motorsports Aluminium cylinder head. Many are coming back on the market as Baby Boomers age and get out of the hobby. With that head getting 250+ hp isn't a problem.

[@jakespeed63]

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

[@Toys4Life]

I need a Willys!

[@racerd9669]

Must give you the willys all that vibration, but low end Tq is amazing for rock crawling

[@Toys4Life]

Indeed.

[@rickybrown8477]

I need one of those intakes and one of those exhaust manifolds for my 87

[@Toys4Life]

Indeed

[@dahirpifo]

What is the size of that rockers? please, o do u have the link. Please please please

[@williambruceboisjoli8455]

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

[@Toys4Life]

Not sure. Maybe somebody else with one will chime in!

[@racerd9669]

My 1988 4cyl automatic car will go 105 and I have never found the real top speed, maybe 112 or so. The car is factory stock.

[@williambruceboisjoli8455]

@@racerd9669 Just asking my 2.5 runs smooth But is the tack way off when doing 65mph my tack is running at 55 rpm should I try getting another tack?

[@racerd9669]

@@williambruceboisjoli8455 My car runs 70mph @ 3000 rpm. Red line is 5400. But I do have a 27 in dia. tire in the rear

[@notbuyingit8047]

How hard would it be to pop an ls head on it?

[@3beltwesty]

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.

[@Toys4Life]

Good point for this at any engine really!

[@HubertJass]

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.

[@Toys4Life]

Good eye! The injectors are even there and ready to go. I am sure Racer D will respond.

[@racerd9669]

@@Toys4Life Yes I did run this engine with the multi port injection and a MegaSquirt 3 system. At the time it had an offset ground crankshaft to use Honda rod bearings , so the stroke was 3.100 and that was 161cu in. . With the port injection and a Hyd Roller cam it made 199Tq and 170Hp. But when I did the change over to the Ecotec engine I upgraded the MS3 to a MS4. So I did not have a computer to run the 186cu in duke.If I get the time I will buy another MicroSquirt and go back to the Dyno with the injection on it. But really what it needs very bad is more cylinder head.

[@pressurevessel8504]

I wish I knew what dist they we’re running. Hei?

[@Toys4Life]

I think that's correct.

[@zedrone7975]

No, but I had techs working for me, I guess I need to dig up the old TSBs dealing with these issues.

[@Toys4Life]

I am sure that the dukes had some issues (and they made a ton of them) but from your experience working at the dealership, the Quad 4 head gasket issues had to be much worse??

[@cccharlie1972]

The 88 iron duke had a balance shaft IIRC. Seems thats whats missing here?

[@racerd9669]

I have a 88 Fiero w the Tech4 balance shaft engine, it really does run smooth. But one thing you have to remember that on the Dyno you are loading the engine as if you were driving up a 30deg grade at WOT in high gear. So the vibration something you would never feel in the car.

[@Toys4Life]

Doesn't that balance shaft cost a fair bit of HP in the duke as well?

[@racerd9669]

@@Toys4Life Yes the balance shaft cost HP and they are tuned for cruse rpm, so when you rev the engine past that point, it actually makes the engine vibrate. That is when it will coast you HP. In the GM Ecotec book on racing the LNF turbo engine, they say it is a 30hp loss at high rpm.

[@Toys4Life]

Very interesting, thanks!

[@cccharlie1972]

@@Toys4Life AFAIK - Horsepower was 92 from 1984 to 1986 and increased to 98 in 1987 and 1988. The balance shaft probably wasn't the only change though.

[@ThorOdinson-zc2kq]

Boy the iron duke was a monumental pos. Thank god they are almost back to the earth.

[@Toys4Life]

We all have our opinions, but it was a very good motor for its intended purpose for sure which was a reliable low revving torquey long-lasting engine.

[@FieroWannaBe]

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.

[@Toys4Life]

Hi, Did you get the flow numbers sir?

[@FieroWannaBe]

I did 230cfm at .600 lift with the Edelbrock intake. 248cfm at .600 with the bare head. There is more info on my RFT build thread. I lost my Pennocks login so I can't post a build thread there.

[@racerd9669]

Any idea what you want for the SD4 head and E intake?

[@FieroWannaBe]

@@racerd9669 I will let you know As I get closer to finishing the build on my Al '801 head. I have to confirm some compatibility differences to be sure I am able to run the AL head on my block as is, and what hardware from the '322 Iron head will work on the '801 head.

[@FieroWannaBe]

@@racerd9669 what where the specs for the cam you had made? My original SD4 cam is a .522 lift, 295 advertised duration, on a 106 LSA. This is a Lunati cam from 1985, 3 bearing core. I was looking at the grinds offered by Isky and like the 292 Mega grind specs for my build. I'm not any expert but have noticed how engines with tight LSAs make power longer on the dyno than ones with a wider LSA.

[@rwdplz1]

Sounds just like my 84 Fiero at idle

[@Toys4Life]

I've had an 84 Fiero and I would agree sounds familiar!

[@carolriley9392]

can you please do this to my Fiero?

[@Toys4Life]

zoom zoom!

[@Blazinpj22]

This motor needs the Super Duty head if you can get one for cheap. People who have those things want an arm and a leg for one. Or do something really insane and try to put an aluminum head on it either from an LS or older LT SBC.

[@Toys4Life]

Super duty head for cheap, let us know if you find one 😉

[@daren9721]

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.

[@Toys4Life]

I believe it has been done and that is an excellent choice! Probably not be the easiest swap though.

[@TeamTORG]

kzbin.info/www/bejne/q3XXq2mpbrNjndU

[@benkalinowski5834]

didn't happen more like 450hp

[@racerd9669]

@@benkalinowski5834 I agree, he needs to get bak to the real world.

[@daren9721]

@@benkalinowski5834 no 450whp, not uncommon research and you shall see

[@racerd9669]

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.

[@Toys4Life]

I did not know that. Why do they flow test under different levels?

[@racerd9669]

@@Toys4Life Well this is where it gets a little confusing. The story I get is that when Holley first started building 4bbl carburetors the flow equipment they had would not pull enough air flow thru the carb, so the reduced the depression to be able to rate the new 4bbl carbs. 2bbl carbs are flowed at 40.6 in of water and 4bbl carbs are flowed at 20.3 in of water.

[@Toys4Life]

That actually makes perfect sense. Thank you!

[@w.peterroberts9624]

It's a boat anchor !

[@Toys4Life]

Yikes

[@mikasantos3774]

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

[@racerd9669]

I appreciate your feed back, and I agree the cam could use a little more duration at .050, if you notice I talk a lot about cranking compression and with 225lbs that is very high for a cast Iron head engine, so more duration would bring that down. One of the problems working with the old Duke engine is finding cam cores, I had to wait almost 2 months to get a core from Lunati and then , the cores are never large enough to get what you want from them. We did not cover the timing changes as well as we should have, but we did try the timing at 28degs it lost power. The major problem holding this engine back is the lack of airflow, I would love to find a SD head. I would think w/o any other changes this engine would make 250 Tq and 250Hp and RPM to 5500. And I also need to get the injection running again, that would take some of the nasty vibration issues out of it, by not shaking the carburetor so bad.

[@Toys4Life]

I'm thinking a small eBay turbo would help the air flow. (:-)

[@racerd9669]

@@Toys4Life But then what is the challenge in that. It would take 20psi to get the HP up to 406hp.

[@mikasantos3774]

I agree with racer D

[@Toys4Life]

@@mikasantos3774 all right, it seems that I'm outnumbered here...

[@uptownsamcv]

interesting

[@mlong5151]

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

[@Toys4Life]

Cool vids on your channel! How did you come to get involved with the Iron Duke?

[@mlong5151]

@@Toys4Life I was running the chevyii with iron head , the rules wouldn't let me run the aluminum arias/ Fontana head, but I could run the Pontiac super duty head, ran across one reasonable $ out of a wrecked Daytona GTP car got a truck block. From the head gasket down the Chevy and Pontiac are almost the same

[@mikasantos3774]

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

[@racerd9669]

3.600 stroke 6.100 rod 4.060 bore and 11.2 to 1 comp ratio. IC closing comp ratio is 7.8 to 1 and cranking compression is 225 lbs and it runs on 92 pump gas. Do you have a cam in mind for these specs?

[@Toys4Life]

Seems like this engine was fully designed on purpose to be a low RPM high torque reliable engine by the original engineers. Makes me wonder if any cam can make that stock head do much better than you already did, unless of course there's a little forced induction action?

[@mikasantos3774]

You could try adding a longer duration cam to help it breathe a little more because those heads are restrictive due to them having swirl ports but try retarding the timing another 5 degrees down to 25 degrees and do another dyno pull with the original camshaft that was already installed swirl Port heads are very efficient they don't need a lot of timing On cam specs I would say .264 at 50thou .600 lift 108 lobe centerline 108 lobe separation

[@racerd9669]

@@mikasantos3774 Well the engine already has too much cranking compression with a 112 LSA, I would be afraid to see what it would be w a 108 LSA. What do you think the Intake closing seat timing might be. Have you spent any time on a flow bench w the Iron Duke head. I have so much time in the heads its crazy. My feeling are it needs more cylinder head. With 192 cfm @ .500 lift. and that is the bare head. If I could get even 250 cfm @ .500 lift. W/O any other changes I would say 220 hp would be easy. It already made 220 tq

[@mikasantos3774]

@@racerd9669 I know them swirl Ports little hard to get flow but I'm starting work on a set of 350 TBI cylinder heads which is pretty much of the same design lots of guys talk down about these heads but you're right about the lobe centerline's 112 lobe Centerline will keep the compression ratio at the little lower cranking compression but by increasing the duration of the camshaft it should let the engine breathe a little more because the valve is staying open much longer for a longer period Of time at that valve lift that u are getting 192 cfm if it's more CFM you are after maybe you should try going to a larger size intake valve and a little more bowl work to suit the valves might get you past the 200 CFM Mark but on the next dyno test like I've mentioned before try playing with your ignition timing below 30 degrees just to find that sweet spot those heads are very efficient port/chamber design those heads are known for a very efficient fuel mileage and torque HAPPY HP HUNTING I know u will find it

[@usedtruckemporiumusedtruck4166]

Dump the induction setup and go for atleast 2 Mikuni CV carbs, but 4 would be better

[@Toys4Life]

I had a snowmobile with Minkuni's on it.. I would go fuel injection - this thing vibrates a lot and it messes with the floats.

[@usedtruckemporiumusedtruck4166]

@@Toys4Life I was personally thinking of the the MJN from mikuni. They're within 10% of the torque of FI, and obviously indistinguishable at WOT

[@racerd9669]

I had it back on the Dyno w Multi port F.I. and it made 235 Tq and 210 Hp and over 210 Tq ever where

[@usedtruckemporiumusedtruck4166]

@racer D it'd force you to lose that manifold. The arbitrary, and unequal length runners are hurting you badly

[@shawnlibby675]

Port the intake in the 2 barrel carbureta for more air..

[@Toys4Life]

I think it's been determined that the head is pretty much the choke point.

[@racerd9669]

I had it back on the Dyno w multi port F.I. and it made 235 Tq and 210 Hp and over 210 Tq ever where. As far as Intake manifold design the EGTs on all 4 cylinders stayed only about 50 degs apart from the start of the pull at 3300rpm until 5500rpm

[@pontushaggstrom6261]

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.

[@Toys4Life]

This was more of a personal challenge. Dave has also played with plenty of Big HP engines for decades and a turbo LNF fiero (check out the vid on my channel). I am not sure, but I think is 8 HP snowblower is now up to 12....

[@racerd9669]

I had it back on the Dyno w multi port F.I and it made 235 Tq and 210 Hp. It had over 200 lb ft tq ever where. NO BOOST

[@pontushaggstrom6261]

@@racerd9669 I mean sure but there are cheaper ways for power

[@racerd9669]

@@pontushaggstrom6261 Its not about the money its about the challenge, if I wanted power I would just cheap out and put a 1000hp shot of NOX on a junk yard 6.2 LS

[@pontushaggstrom6261]

@@racerd9669 well that would blow up your engine. Indeed n/a tunign is a lot more fun and challenging

[@lordflick895]

I kind of want to see that go into a Camaro now lol

[@Toys4Life]

Ummmm, maybe not - too heavy?

[@lordflick895]

@@Toys4Life oh it would still suck but at least not like the 82 Camaro that came with the stock iron duke.

[@fierofrank3062]

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)

[@Toys4Life]

Shops like this are getting few and far between!

[@larryblack4257]

Should of showd the motor 8m sure u sold it by now

[@danawick9817]

maybe a slightly smaller carb woud work better

[@Toys4Life]

Hey, everything's worth a try for sure! I think the harmonics and the vibration of the engine were messing with the floats at certain RPMs.

[@HeckyReckyOfficial]

the intake manifold looks like a huge problem. very turbulent with no consideration for harmonics

[@Toys4Life]

Hopefully Dave comments - I think there may be an issue there as well - but the head is also a weak link 4 sure.

[@HeckyReckyOfficial]

@Toys4Life the head suffers from 70 year old architectural design philosophy, dont worry about that. Get the runners equal, look up the hemoholtz effect and use that to dictate runner length. A single carb set up will require a plenum. A dual carb set up will still benefit from scavenging between cylinders but be easier to develope a manifold for.

[@robertballenger3806]

I bet theyll hit 280 with a turbo

[@racerd9669]

Robert I had it on the Dyno last Sat. W the multi port FI and a MicroSquirt ECM. It made 235 Tq. and 210 Hp @ 5300 rpm. It had over 200 lb ft of Tq ever where.

[@anthonymacaluso1488]

Just add a little boost and wa-la 200 easy

[@Toys4Life]

indeed

[@prjndigo]

so its not an iron duke nor is it a 2.5 ... good job. downvite

[@Toys4Life]

It is an Iron duke block and head.

[@boxfancb]

172HP on gas is good enough for me.

[@racerd9669]

Well I had it on the Dyno w the Multi port FI and a MicroSquirt ECM and it made 235 lb Tq @4300 and 210 Hp @ 5300. It had over 200 lb ft of Tq ever where.

[@boxfancb]

@@racerd9669 I take my hat off to you👍

[@imtheonevanhalen1557]

Oil pressure is way too high.....anyone who's ever tried to drive an oil pump with a drill etc.....parasitic loss is incredible. 10 lbs. per thousand RPM's for oil pressure is MORE than enough.

[@johnpublic168]

Carb and induction is killing the power

[@Toys4Life]

I think it's established that the cylinder head is the weakest part. Who's got a super duty head to sell?

[@MidnightinSavannah]

@@Toys4Life I had a friend of mine who sold his not too long ago. I can found out who he sold it to.

[@paulsypersma7165]

Aluminum,gets too hot

[@Toys4Life]

What part?

[@benjaminmeadows1380]

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

[@Toys4Life]

400k...oh my

[@Gtrips07]

K swap it

[@racerd9669]

I LNF swapped it.

[@Toys4Life]

I wouldn't mind doing it turbo intercooled 4 cylinder either a Honda or an ecotec.

[@zedrone7975]

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!

[@racerd9669]

I think you may want to do some research, there are plenty of Iron Duke engines that over 200,000 miles and are still running strong.

[@zedrone7975]

@@racerd9669 I have plenty of research, over 20 years worth 78'-2000' as G.M. at a Chevrolet dealership

[@racerd9669]

@@zedrone7975 So where you a line mechanic for GM?

[@aaronmcilvain8077]

Well the race version called the SD4 dominated all its competitors in IMSA GTU in the back of a Fiero

[@zedrone7975]

@@aaronmcilvain8077 Yes you are right, but that's a completely different animal than the production engine

[@joserribera4888]

Can u text me and help me do the same to my iron duke fiero

[@racerd9669]

Jose if you need help I would be glad to help you out.

[@Toys4Life]

Jose left the chat?