Seems like there's lots of things you can do to the 2.8, but I've never really seen the little iron duke talked about too much here. So, I'm wondering what can be done to it to increase performance, and also where to get the stuff from. Aside from boring it out, and shaving the head, what else can we coupe owners do? Add on's, etc? I mean, we only get 90 something horse from what I understand, I want more.

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[This message has been edited by FieroFanaticus2 (edited 06-14-2006).]

The consensus seems to be that the duke isn't worth upgrading. It won't withstand much of a power increase before it comes apart, and engine swaps are much cheaper and provide a better bang for the buck than attempting to upgrade a duke.

There have been dozens of threads regarding increasing the duke's output....none have turned out well.

Sorry....I know it probably isn't what you wanted to hear.

yep, the duke is a commuter engine. it was really good at its time. the bottom end won't handle a turbo. 92-98 hp will get you around ok. you can get a tune up, k and n air filter, gut the cat, synthetic oil, might get you up to 100 hp? good coat of wax to slide down the highway!?

probably be better off with a 2.8, 3.4, 3800sc or a sbc if you want to get well over 100 hp out of your car.

sorry i wish there was something to do.

quote Originally posted by sostock: yep, the duke is a commuter engine. it was really good at its time. .

It's important to place things in their context in time. When the duke was built, it had a similar output of most other economy engines of the time. Yes, it's small compared to today's offerings, but in it's time, it was right on par.

If you just want an inexpensive boost in power, swap in a stock 2.8. There are an abundance of them, and for the 85-88 cars, it doesn't take a whole lot of effort...and it's about a 40% increase in power over the duke.

Like everyone has said, the 'duke is simply not capable of withstanding much more power than it currently produces.
If you're concerned about gas mileage but want more power, you might look into the Quad-4. It should give near identical mileage, but 160-190 HP.

quote Originally posted by Jax184: Like everyone has said, the 'duke is simply not capable of withstanding much more power than it currently produces. If you're concerned about gas mileage but want more power, you might look into the Quad-4. It should give near identical mileage, but 160-190 HP.

Is the Quad a bolt in replacement? Will it bolt up to the dukes transmission or would he need to change tranny or use a plate? Anyone know of any other GM 4 cylinders that would replace the 2.5 (maybe the 2.0)? I had a 2.0 in a Cavalier that seemed to pull the car well with a 5 speed. Just some thoughts, I haven't messed with 4 poppers much myself except for servicing them at a shop.

The best performance upgrade for a duke is advamnce the base timing about three degrees.

The Quad 4 swap is as complicated as any other swap.

The easiest swap is to convert to a 2.8. 3.1 or 3.4 V-6 using all Fiero accessories. This of course assumes thahe car is not an '84 so that a fiero V-6 ecm harness will plugg right in..

if I had an 84-86 duke, I'd just 4.9 it.

for the 87/88 there's always the Grand Am Duke swap for a 14hp gain...

Check the archives for a 195 hp duke build up...

Not to nit pick, but isnt the duke more like 70whp?

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1986 GT, LT1/4T60E. In the middle of cam/port, new interior, paint and waiting on new wheels. Itll blow you away!!
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Its easy, use the 2.5 as an anchor and get an engine that has 3 digits in the hp rating.

the engines are weak but things can be done to it to get little power increases. from what I have seen of the fiero duke is that the intake is very restrictive and the stock lift is very far from where the power is. You have the mercury 3.0 crank, sbc pistons and rods, higher ratio rocker arms and a variety of camshafts. Yea the power output of the duke will never be as good as a v6 or v8 and it does take alot of money to make one decently powered but getting 180-200hp will cost ya but the shock factor is worth it. Im in the middle of working on my duke and will be putting the money into machine work and sleeving the block and using the 3.0 crank and hoping for about 3.2 displacment when im done, though going a 3.4 would be better for what I will be using it for but not for the powerband I need it to work at.

The Quad-4 is a bit of work, but one day I hope to have the money to do it myself. Getting comparible power out of a 'duke would probably cost as much, and give you an engine that still has a laughably weak block and unimpressive gas mileage.

quote Originally posted by lou_dias: if I had an 84-86 duke, I'd just 4.9 it.

Yeah the Duke was decent in it's day, you have to remember that small blocks were only making like 170-200 hp in the 80s.

The 4.9 is an awesome upgrade for a duke. Double the horsepower, gobs of torque and not much heavier. Fairly straightforward installation. The 4.9 is not for everybody, but you could drop one in a lot easier than trying to get a duke to run ~200 hp reliably.

take it from someone who's still strugglin' with a couple of dukes himself, just use it for what it is till you can work out something else. everything i've read says a duke is good for about 140hp at best without losing total reliability, about what you'd get from a 2.8 anyway. and having a 2.8 also, putting that kind of money into a duke to equal a 2.8 is not much to aspire to.

i think the only people who have done it happily are mechanics who have the free time to play with them without too much cash investment. if you don't fall into that category i can't see it being worth it.

Try this web site by Ira Crummey. Ira has done a nice job posting great info on the Iron Duke:

http://ironduke7.tripod.com/builtduke.htm

Links to the above site and hundreds more Fiero-related sitesare at our web site:

http://fierosails.com/fierosecrets.html

Paul McKibben
fierosails.com

quote Originally posted by lou_dias: if I had an 84-86 duke, I'd just 4.9 it.

From one boat anchor to another huh????

The 4tech can produce power with the right parts. The crank is weak and will not hold much power. This does not mean you cant mod it to get more out of it. Yes there is ways to get cheaper power. I am going to build a 2.5 here soon, not for killer performance, but better performance. I think the wow factor of a 2.5 performing is better than a known performance engine performing (like a 3800s/c or a sbc).

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