I love my '85 2M4 coupe, and I like the simplicity of the powerplant. However....

I'm intrigued by the mission of getting some horsepower out of it. I know I could drop a bigger engine in, and I know that GM never got more than 98hp out of the stock engine. Any ideas on bolt-on mods to threaten the century mark? Don't own a milling machine or serious shop, but my wife (god bless her) lets me indulge my hobby. And she likes the car.

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tucsonsean

The only thing i could find was a header. other than that you risk blowin the whole thing up!

there is available a bolt on throttle body and intake manifold branded by holley that could do it.
there is also the carbuerator intake manifold by edelbrock and a carb you could bolt on.
as far as there being a custom 4 pipe header for the duke, there is the hooker header, and maybe one made by someone here on the forum.
Also some big block roller rocker arms to make lift and duration consistent.
other than that. theres nothing else. unless you decide to start machining and rebuilding it. then everything opens up.

quote Originally posted by AL87: Also some big block roller rocker arms to make lift and duration consistent. other than that. theres nothing else. unless you decide to start machining and rebuilding it. then everything opens up.

Did the 85 have roller rockers?

quote This was replaced by a swirl-port head with 9.0:1 (instead of 8.2:1) compression ratio in 1984 for a 2 hp (1.5 kW) gain. Other additions for 1985 included roller lifters, improved bearings, and a new crankshaft.

I guess so .

There isn't much you can do to get more power out of the Duke. Even the Edelbrock intake and carb isn't going to be much if any improvement. You'd be going from a more efficent fuel injected system to an older carbed system. The Holly intake and TBI might be a little bump up in power, but again not a whole lot. A cold air intake is pointless as the Fiero already uses one. The best things are to make sure the ignition system is in tip top shape. Older plugs, wires, distributor and such can rob power. A free'er flowing exhaust might gain you a few more HP, along with the headers mentioned adding a few more. I think stock the Duke was rated 92 HP? So it's not that large of a power increase to get to 100. One thing I've heard done, although it takes a little bit of modding, it getting the head from a S10 that used the Duke since it has a free'er flowing deisgn. You could also port match your intake and exhaust to gain a little power to.

There used to be a website that outlined how to mod a Duke to get to different power ranges. I think he went up to over 170 HP from a Duke, but the expense just grew and grew and the mods just got more and more in depth to the point of no longer being street legal.

Honestly the Duke wasn't made to make big power, it was made to get good mileage. Being a 25+ year old engine, it doesn't have the advantage of technical progress that current engines have. So it really doesn't lend itself well to the kind of gains current engines can get.

Oh, and whatever you do don't buy a "Super Chip" for it. All it does is dump fuel in the engine killing your economy without giving you any measurable power gain.

[This message has been edited by Khw (edited 04-26-2012).]

If I had a Duke, I would personally not waste any money in trying to get power from it, and instead start saving up for an ecotec motor. They are 1000% times better, just as efficient if not more so, and you still have a lightweight powerplant. There is plenty of aftermarket support and bolt on goodies for the Ecotec from ZZP as opposed to wasting money on DDP (Delusional Duke Performance )

Your question has been covered many times on PFF- check the archives

I've heard the application of the correct stickers can add 10-15 hp

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Dave

www.ltlfrari.com

quote Originally posted by Khw: There used to be a website that outlined how to mod a Duke to get to different power ranges. I think he went up to over 170 HP from a Duke, but the expense just grew and grew and the mods just got more and more in depth to the point of no longer being street legal.

This web site has some info that's been around for a while: http://ironduke7.tripod.com/IronDuke.htm

Yes some 84s and 85s had roller lifters. Most were the result of recalls involving eng replacement. As I understand it, toward the end of the production year of 85 they started putting them in at the factory also. I've had two 85s and one 84 that had rollers.

[This message has been edited by 2farnorth (edited 04-26-2012).]

I like the simplicity of the 2.5 as well.
Upgrading to the early 90s S10 head/intake would be an improvement. But there's more parts needed to do that conversion on a pre-87. From what I remember you have to replace the head, intake manifold, TBI unit, throttle cable, and adapt the sensor wiring to the new TBI. I think the exhaust manifold will transfer.
I've heard of people making adapter plates for the old intake to the newer head, I saw some conversation about that on an S10 forum.

The Holley parts mentioned were designed for the pre-87 engine but they're hard to get nowadays. There's also a performance cam available, I had the flat tappet one in my 84SE but there's also a cam for the roller lifters. That would boost your peak paper hp but it's a tradeoff in real driving.
Mine was an auto and it had about the effect you'd expect - it was kind of iffy at low RPM but ran well at 3000rpm+. Before the cam swap, a full throttle induced downshift would actually make the car feel like it was engine braking at 4500+. After the cam, it was more willing to rev but was more peaky. Low RPM performance was inconsistent so I know it had other problems, but I didn't know very much back then.
Anyway, the cam is a torque curve "adjustment" that some may like and some won't. I'm sure it does hurt gas mileage but I don't know how much, I didn't keep track of it back then.

There's an intake manifold for the SD4 that comes up on eBay a lot (or at least it used to). I don't know if it bolts up to the Duke head, and it mounts to a carb and has no provision for EGR. I have no idea if it would be useful.
The Holley intake and TBI rarely come up.

I don't think there's anything that "bolts on" that will make much of a difference. You could put on a turbo, but you'd have very short enjoyment of the increased power, because the engine would blow in short order. But if you could rebuild it with 88 crank and rods (they're stronger), a later model head (flows better), and a mild cam, you could get 120HP out of it.
Stock dukes from the last couple of years it was made put out 110-115 HP.

As said, anything you do for more power is going to shorten the life. Bolt on a nitrous system.

I think the best performance you would get out of a Duke is bolting on a chain and using it as a 300lb boat anchor.

I just noticed an interesting thing on this site http://ironduke7.tripod.com/IronDuke.htm

The guy says if you run higher octane fuel then you can advance the ignition timing and therefore get more power and fuel economy. Here in Europe after converting the US octane units to ours we still have a little bit higher octane fuel as standard(95 octanes which in US rating is about 90, I'm guessing standard in USA is 85?). So after advancing the ignition timing can I get any measurable gains in fuel economy or power/torque?

I have an '85 auto and our emission policies aren't as restricting as the US ones. So taking that out of the equation is it still worth doing? And by how many degrees should I advance it if it works?

[This message has been edited by cebix (edited 04-26-2012).]

If you want any significant increase in power you need a new head or go turbo. There are just no bolt ons that will make much of a difference. At most, a normally aspirated Duke will make 120hp with the original head.

quote Originally posted by cebix: Here in Europe after converting the US octane units to ours we still have a little bit higher octane fuel as standard(95 octanes which in US rating is about 90, I'm guessing standard in USA is 85?).

Standard in the US is 87.

quote Originally posted by 2.5: Standard in the US is 87.

So I guess there is pretty much no difference then.

I was planning on modifying my duke as well because my friends dad has a heavily modified duke in his 84. My main reason for getting a 4cyl fiero. What I didnt know is he machined the crank and cam himself, he is running close to .8 inches of lift, holley TBI and intake manifold, custom headers, lots of head work including bigger valves... The thing sounds sick, has a really different sound like a braap kinda sound you would associate with a dirtbike almost. His cost of everything is extrordinary, and he has like 150 hp tops which is decent... but he always has to worry about the block cracking because the block is so weak. When I get home I have my old duke taken apart I will show you how thin the cylinder walls are. He has gotten that much HP out of the engine because every piece from the inside is no longer stock and alot of it is custom. I ended up swapping a 2.8 because lots of people swap new engines in and sell the 2.8s for cheap and because I want to keep a fiero engine in my fiero. It is a stronger engine for sure, people are running 200+ hp with stock internals so even though it is still gunna be expensive to upgrade, at least there is aftermarket support and the engine can actually hold the power. The Iron duke just cant, so If you are happy with like 120 hp then stick with the duke and do some upgrades. If you want more, then itt will cost exponentially more money and you can only go so far.

quote Originally posted by cebix: The guy says if you run higher octane fuel then you can advance the ignition timing and therefore get more power and fuel economy.

I've advanced the ignition timing on my '84 considerably without using anything other than regular gas. Whatever the last number/notch on the timing plate is, that's what I've set my timing to (with the jumper in place). It idles a little rougher with the timing this far advanced, but the tradeoff is worth it IMO. Better gas mileage, better performance, but I suspect it runs "dirtier". (I set the timing back when I go through the annual smog test.)

Just be VERY careful your engine isn't pinging if you try this. Every engine is different. What works for my duke may not work for yours.

[This message has been edited by Patrick (edited 04-26-2012).]

quote Originally posted by Patrick: I've advanced the ignition timing on my '84 considerably without using anything other than regular gas. Whatever the last number/notch on the timing plate is, that's what I've set my timing to (with the jumper in place). Better gas mileage, better performance, but I suspect it runs "dirtier". I set the timing back when I go through the annual smog test. It also idles a little rougher with the timing this far advanced, but the tradeoff is worth it IMO. Just be VERY careful your engine isn't pinging if you try this. Every engine is different. What works for my duke may not work for yours.

Can you tell me more about the gains? Have you measured your mileage/dynoed your car/did 0-60 runs or something else?

I remember when I changed the fuel filter and it felt like I gained a LOT of HP(the old filter looked like it was original to the car) but trying out the car 0-62 MPH i dropped only 0.3 seconds from 15.7 to 15.4. Very easy measuring thanks to the automatic gearbox. Yeah my duke is very slow.

[This message has been edited by cebix (edited 04-26-2012).]

quote Originally posted by cebix: Can you tell me more about the gains? Have you measured your mileage/dynoed your car/did 0-60 runs or something else?

For whatever reason, the fuel economy has always been lousy with this duke. It runs very well, but keep in mind I live in the city and most trips are rather short. The best mileage I've ever gotten is perhaps 25 mpg on the highway.

I'd say I get an extra 20-30 km on a tank of gas (the 84's have the smallest tank) with the ignition timing further advanced. I autocross my '84, and I definitely feel (and hear) a difference with the way second gear pulls (swapped to a 5spd) on the track with the advanced timing.

It doesn't cost anything to try... but listen carefully for the pinging! You don't want to wreck your engine. A functional EGR is mandatory.

[This message has been edited by Patrick (edited 04-26-2012).]

quote Originally posted by Patrick: For whatever reason, the fuel economy has always been lousy with this duke. It runs very well, but keep in mind I live in the city and most trips are rather short. The best mileage I've ever gotten is perhaps 25 mpg on the highway. I'd say I get an extra 20-30 km on a tank of gas (the 84's have the smallest tank) with the ignition timing further advanced. I autocross my '84, and I definitely feel (and hear) a difference with the way second gear pulls (swapped to a 5spd) on the track with the advanced timing. It doesn't cost anything to try... but listen carefully for the pinging! You don't want to wreck your engine. A functional EGR is mandatory.

That can be a problem, my EGR wasn't working at all so I just disconnected it altogether from the engine and put a thick metal sheet in it's place to cover the manifold hole.

It was so bad that when the auto shifted to third you couldn't keep driving along at one speed because after a few seconds the engine would buck back and forth like it was about to stall. Should I get a working EGR or can I advance the timing without it altogether? The engine runs very smooth and quiet, no bucking, nothing.

And I thought my MPG was lousy. I get about 25 MPG part city part highway but it's an automatic.

[This message has been edited by cebix (edited 04-26-2012).]

I have had 2 iron Duke Fieros. They had ported head, Holley TBI, Holley intake, Hooker Tri-Y header. I also installed roller rockers (not just roller tip).

The performance return was not worth the money I invested. The best you will achive safely is about 115 to 120 HP. The best part is mpg is not afected much You will still get about 28mpg on the road. I recently got a GT and the differance in performance is amazing , even for a stock, auto 2.8.

[This message has been edited by fotofrank (edited 04-26-2012).]

quote Originally posted by cebix: That can be a problem, my EGR wasn't working at all so I just disconnected it altogether from the engine and put a thick metal sheet in it's place to cover the manifold hole. Should I get a working EGR or can I advance the timing without it altogether?

I think if you look into how an EGR works and how it affects an engine, you probably wouldn't want to push your luck by doing what I've done without a functional EGR being installed. I'd be hesitant to do it.

I always thought that the EGR was just an emmissions cleaning device that worked by pumping some exhaust back to the intake to let it burn some more and therefore clean it up. Guess I'll have to look at what it really does.

[This message has been edited by cebix (edited 04-26-2012).]

quote Originally posted by cebix: I always thought that the EGR was just an emmissions cleaning device that worked by pumping some exhaust back to the intake to let it burn some more and therefore clean it up. Guess I'll have to look at what it really does.

The way I understand it is the EGR opens up and the vacuum from the intake sucks in exhaust, and it's used as a filler in the intake and combustion chamber so it uses less gas while cruising. On engines the like the 2.8, the ECM also changes timing when it opens up the EGR. On the Duke, the ECM has no control over the EGR system.

Also, I get about 17 mpg city on average...but that's with a V8.

[This message has been edited by mattwa (edited 04-26-2012).]

Egr is an emissions thing but thats not how it works.
In low load conditions the egr valve opens and adds exaust gas to the combustion chamber in the place of some of the intake air that would have entered. This makes the oxygen concentration of the combustion chamber lower allwoing the ecm to lean the fuel mixture out a bit without removing timing (and without detonation)
Edit also what he said^^

[This message has been edited by gtjoe (edited 04-26-2012).]

Get a helper to see if TBI can reach WOT when gas pedal is pushed...
see my cave, throttle Cable in general engine section.

ECM doesn't have EGR control but ECM maps are calculated for EGR working. Removing EGR can cause problem.

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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)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

All very interesting...and informative. It's hard to believe that in 30+ years, hundreds of applications, in dozens of models, more hasn't been created to enhance the old Duke. I guess I can live with 92hp. It may not smoke anyone on green, but once in motion, it's still great fun to drive. And it's no more underpowered than the Brit sportscars I used to rebuild--and they were great fun, too.

In the meantime, I'll browse for the Holley intake and TBI, maybe some headers, a free-er flowing cat, and some other fun bits that I can tack-on in my driveway.

Thanks, everyone. (and I'll check your throttle cable info, Ogre.)

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tucsonsean

[This message has been edited by tucsonsean (edited 04-26-2012).]

quote Originally posted by tucsonsean: All very interesting...and informative. It's hard to believe that in 30+ years, hundreds of applications, in dozens of models, more hasn't been created to enhance the old Duke. I guess I can live with 92hp. It may not smoke anyone on green, but once in motion, it's still great fun to drive. And it's no more underpowered than the Brit sportscars I used to rebuild--and they were great fun, too. In the meantime, I'll browse for the Holley intake and TBI, maybe some headers, a free-er flowing cat, and some other fun bits that I can tack-on in my driveway. Thanks, everyone. (and I'll check your throttle cable info, Ogre.)

What is there to enhance? it was designed and built purely for economy only, and it does a great job of it. The internals are weak, it's heavy as hell (only 50lbs less then the 2.8), and even by the standards of the 80's was pretty poor of an engine in general. But of course that's my opinion.

re timing
On my 2.5 I pretty much ignored factory spec and used more advanced ignition timing, I just listened as I drove and backed it off if I heard any knocking. It was easy to hear on that car with the sunroof up. I also used 89 octane to help with it.
I never dynoed it or anything, but just from how it felt driving it, it was more responsive at low RPM when it was more advanced.
I failed the visual portion of my first CA emissions test because they saw the timing was wrong (they're picky about that stuff here). Up until then I didn't even have a timing light, and after I put it back to 8 degrees it felt sluggish. As soon as it got tested I advanced it again.
Every engine is different though, and mine was far from factory fresh condition. I wouldn't be afraid to experiment, but listen to it under load for pinging. Going uphill with a hot engine is a good time to be listening.

quote Originally posted by armos: re timing On my 2.5 I pretty much ignored factory spec and used more advanced ignition timing, I just listened as I drove and backed it off if I heard any knocking. It was easy to hear on that car with the sunroof up. I also used 89 octane to help with it. I never dynoed it or anything, but just from how it felt driving it, it was more responsive at low RPM when it was more advanced. I failed the visual portion of my first CA emissions test because they saw the timing was wrong (they're picky about that stuff here). Up until then I didn't even have a timing light, and after I put it back to 8 degrees it felt sluggish. As soon as it got tested I advanced it again. Every engine is different though, and mine was far from factory fresh condition. I wouldn't be afraid to experiment, but listen to it under load for pinging. Going uphill with a hot engine is a good time to be listening.

You're kidding, they looked at the timing and it failed?! My gawd...never ever moving to CA.

when and if I plan to rebuild my duke, im putting a mercruiser 3.0L crank in it (stroking it to 2.7L effectively) (strongest crank available before entering into performance options.)
im going to use late model duke connecting rods. (and I will not bore the block any at all, unless I get an SD block) (again these are the best stock rods, otherwise in the SD4 manual go with small block chevy rods)
the main differences are in the head and cam. SD head is best, the closest you can get to that (while keeping it simple) is overporting the stock head (bigger valves too), intake and throttlebody along with a long tube header for exhaust scavenging. and I think a cam that lopes a little like a 260* duration would do just fine.
flat lifters are great for low end rpm, roller is good for high. to make the power, the duke must rev high, but it sacrifices low end torque.

the problem here is that people want Horsepower. that is the wrong way to go, make the duke Torquey
listen here from the 1:00 to the 1:20 mark in reference to torque http://youtu.be/4BJJ3DHs5cs
the cosworth 16valve head sacrificed the torque. as with most 16valve engines today they perform best at high rpms.

and as others have said, keep your ignition system in tip top shape, I myself am using an MSD-6AL control module with an MSD blaster coil (cylindrical shape) I am also using a cap and rotor with gold contacts with an upgraded style distributor. I may for the purposes of service life upgrade the plugs from stock copper electrodes to irdium. and upgrade the wires to 10mm racing ones. (stock wires are getting burnt up)

I've got all the practice I need with the porting and polishing and port matching, but I will overbore the throttle body, the intake manifold, and the head. Make that head flow!

Yeah I assumed that the EGR in a petrol engine does the same job as in a diesel. It's just there for ecological purposes(burning again some exhaust so that more fuel is efficiently burned). Didn't know there are actually maps in the ECU for that and that it allows for leaning out the mixture.

[This message has been edited by cebix (edited 04-27-2012).]

25 mpgs in a duke is bad, even an auto. If tuned good even a very worn out duke should pull 30-32 on the highway IMO.

Anyone that spends money trying to rework the Iron Puke when the easiest hop up is to just fit a stock Fiero V6 is a fool. IMHO, of course.

Why the animus? I know the v6 would be easier, but it wouldnt have stimulated such interesting discussion. As the'fool' who started this thread, I have to tell you that I was never looking for 'easy'. This is my hobby and I shoot for 'interesting' and 'challenging.' And I want to end up with something I can work on in my driveway Saturdays with a modicum of tools and skill.

quote Originally posted by tucsonsean: Why the animus? I know the v6 would be easier, but it wouldnt have stimulated such interesting discussion. As the'fool' who started this thread, I have to tell you that I was never looking for 'easy'. This is my hobby and I shoot for 'interesting' and 'challenging.' And I want to end up with something I can work on in my driveway Saturdays with a modicum of tools and skill.

Ignore them. Some people are saying it will cost more than you gain, that is one thing. Some people rag on the duke because they think they are cooler for having a larger faster engine. Same thing with some folks only info fastbacks, a notchie is beneath them. Same thing for V8 vs. V6 ....More power to ya I think to myself, we like what we like, spouting off about it isn't impressing anyone.


If I were you I'd check out the super duty 2.5 liter:

"Though not a production engine, the Super Duty 4 racing engine was notable and widely publicized at the time. It was the basis for NASCAR's Touring Car series. The Super Duty 4 (usually called the "SD4") is still in use today for ARCA Racing.

A 2.7L 232 hp (173 kW) SD4 engine powered the 1984 Fiero Indy Pace Car to over 138 mph during the race. The SD4 was never available in production vehicles, however Pontiac's Performance Parts counter had all the SD4 parts available and one could garner a 2.7L 272 hp (203 kW) version and a 3.2L 330 hp (250 kW) version. All 2000 Indy Fiero replicas came with the 2.5L 92 hp (69 kW) Iron Duke engine.

The SD4 was the last in a line of high performance Pontiac "Super Duty" engines. Kansas Racing Products still makes the engines after buying the rights to make them from GM.

Cosworth also produced a 16-valve head (Cosworth Project DBA, 1987) for the Iron Duke.[1]"

-wiki

you wouldn't happen to have that link to Kansas, hum?

[This message has been edited by E.Furgal (edited 04-27-2012).]

quote Originally posted by E.Furgal: you wouldn't happen to have that link to Kansas, hum?

http://kansasracingproducts...roducts/Welcome.html

Yeah and about the notchie vs fastback... Am I the only person in the world that doesn't like the fastbacks? I just think the notchie has an original line to it and looks very american to me. The fastback looks like a Ferrari wannabe to me. I don't want to upset anybody who owns a fastback but just wanted to add my humble opinion... and hopefully not derail the thread.

Any thoughts what can be done to my 2.5 to restore back some power and MPG? I did a whole service when I bought it - spark plugs, wires, new cap, rotor, coil. The oil in it was a mess. The oil was pretty much rubber under the valve cover so I guess there's some stuff inside I don't want to see. Is it a good idea to take it apart without any replacement parts like piston rings etc., clean it up and put it back together? Or should I just rebuild it when I'm at it?

Oh and I put it a K&N air filter. No noticable difference but at least it should last forever.

[This message has been edited by cebix (edited 04-27-2012).]

quote Originally posted by 2.5: http://kansasracingproducts...roducts/Welcome.html

thanks,, I think a 2.5s/d with a <cring>mopar 2.2 turbo a mistu intercolloer or u r a bus .. would make a set up that go nicely..
I'd really really like to get my hands on a HHR echotech turbo drivetrain.. that would push these lite cars allong nicely..