I recently replaced the stock ignition module with an accel hi po module. I wouldn't say the car has too much more power, but it definately has more power in the higher rpm's than before. After about 4 grand it didn't really have any power any more go, but now I could probably go right on up to 6 or so. Any suggestions on how high the old duke can be safely run?

Ryan

See that red patch on the tach.... it's there for a reason. The duke was not built to be spun way up. It can be built up to take more but I wouldn't be beating a stock one too hard.

I have always been told that anything above 5,000 was living on borrowed time but plenty of folks have war stories of 5500++ from the Duck.

How high do you really want to take it?

The duke is half of a 305, so it's theoretically possible to make it do a lot, if you have the $$.

The rev limit is probably due to valvetrain float, so good roller rocker arms (Friction loss and weight savings), stronger springs, seats, etc. will probably allow you to lift that somewhat. I don't know how the lifers react to all of this totally, but it would seem that they would need to be kept in line, or some way found to reduce their motion.

IMHO, building up a duke to do fun things has its own set of bragging rights, but I think it would be less of a headache to put in a Q4 or some other engine, and spend your sanity on driving the car. Just my 2 cents, and probably not adjusted for inflation.

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Actually, the Iron Duke is not half of a 305. The 305 is a Chevy engine and the 2.5 is a Pontiac motor. Two different design paths altogether. It would more closely be considered half of a 301. It's also the last engine Pontiac made.

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We all come into this world the same way; naked, screaming, and covered in blood. If you're lucky, it doesn't have to end there.

See http://www.homestead.com/Fiero2M4/IronDuke.html

So I have read, the Duke's crank and block are weak, and can't reliably take more than 5,000. I believe it; the Duke's design looks Opel-ish, and I have seen a few scattered Opel engines.

Weak crank and very weak block. Remember, they were designed as an economy engine. I've heard that the 90-91(i think) S-10 2.5 crank is stronger, but asking the duke to rev above 5g's is asking for trouble, imho. You'd probably be better off going for torque. In stock form it only has 20ft/lbs less torque than the S-2000... no replacement for displacement

[This message has been edited by Standard (edited 02-11-2001).]

I let another Fiero owner drive my 88 w/iron duke. He brought it up 2 4500 and the next day I had lower oil pressure and it had a spun bearing I did install a v6 when that happened though

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Josh
88 Coupe V6

My pics

My brothers Grand AM with the 2.5-liter engine redlined at 5500 rpm. That was the 2.5-liter motor with the balance shafts and it made 110 horsepower and 135-ft. lbs. of torque. He also beet the hell out of that motor redlining it all the time and racing other cars, surprisingly it never let him down in the three years he had it.

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It also depends what year 2.5 you are talking about.... the 87 and up motors are significantly diferant than the older blocks.

F88; If the duke is half the Ponti 301 (4.8 Liters) how come it's a 2.5, and not a 2.4? I suppose a little extra stroke would do it, so I'll have to ask my mech. The 60° V6 (The 2.8 in yours and my Formulas) is a Chevy engine, with reworked intakes and heads, from the S-10 and the Citation X-11.

And then there's the Super Duty, which, as I understand (though I haven't researched this as much. They don't seem to be available new anymore.), is the duke, bored out with performance parts. GMPP still offers some parts for it.

Ogre; I thought the 2.5's were all the same, except for the DIS (Direct [or, Distributorless?] Ignition System) of the '87-88's.

DIS required a diferant block casting and crank. In order to consolidate part #'s durring manufacture it looks allot like GM used the same block in all 2.5l DIS applications, including the S10. I'm not sure if all applications got the same crank. One of these days I'll sit down with some engine parts books and see just what varies from on application to the next on the DIS motors.

Well, a 2.5 would be half of a 302, being it has a 4 in bore and a 3 in stroke. But it really isn't a modified v8 design. The port layout looks similar to a SB2 chevy head also. Lots of things about the motor says that it's able to make lots of power, but the parts aren't strong enough to take it.