I think it is nothing new to anyone here that these blocks extrordinarilly weak when you push it for extra HP.

however. since i have not personally experimented with pushing one of these motors past its limits. i was curious what those who had can report.

i know there are many sturdier parts that can be replaced to make the motor stronger. cranks, rods pistons, cams, etc. but those are only as strong as what the block itself can take.

I seem to remember one person suggest a while back. that the blocks strength was greatly inhibited by very weak mains bolts and head bolts. however i would think that if it were this simple, that many out there would have remedied this a long time ago. if it is true though, how much more will this allow the block to maintain power wise.

also , i have heard people mention the 86 s10 duke block, what makes it "beefier" as others seem to say it is?

just looking over a fiero duke block i would hazard to guess that the main caps are a major problem. but i am wondering if it is possible to add custom main caps that are 4 bolt rather than 2 bolt mains, similar to what you can do with a sbf 351 clevland.

i know KRP makes reproductions of the SD4. i am wondering if their main caps would work on a stock duke. or if it is not too outrageous to have custome main caps made.

does anyone know if there is enough solid meat in the 2.5 block to drill for 4 bolt mains.

i am just wondering if there is potential for this block with some reinforcing to get it to crest 200-250hp without grenading. if it is possible, there could theoreticly be a revival for this motor similar to what has happened with the F.E. for blocks that in the past nobody wanted for even boat anchors.

i am probably way out in left field, but i like thinking out of the box sometimes, and am curious what others think.

Roland the Duke engine uses a very thin block casting, lightweight rods, and a light duty crankshaft. The Duke was not designed for performance. If performance is what you want, spend you money on an engine swap. You'll get more horsepower per dollar spent.

The major thing is that the entire block is conducive to flex, and it has very thin bulkheads and deck surfaces. The head and main cap bolts, for example, are not a problem. In fact, KRP uses 2-bolt mains themselves, even in their ARCA racing engine applications, which frequently run at 10-11K RPM. I will be running 2-bolt mains myself with my turbo SD.

Simply adding 4-bolt mains to the regular 2.5 block will not accomplish anything. The block is of a design which has several inherent properties that simply make it not well applied to performance, nor is it very well modified.

Nate

------------------

My Web page | The Turbo Super Duty Build.
You know that little voice that says it can't be done? I duct-taped mine's mouth shut and pushed it down a flight of stairs.

The distributor blocks are known to crack in certain areas. One of the recall documants had you looking for cracks long way across the lifter galery.

------------------
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.
(Jurasic Park)

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

well, i guess it is as hopeless a block for mods as most say it is. I guess there are more differences to the SD block than meet the eye upon initial glancing. It's just that when i first looked over a SD block i saw no major differences to the stock block, yet the SD has been known to handle 400+ hp.

I suppose the best alternative would be to cough up $2,500 and buy a KRP Super Duty 2.5 block. I dont care much for their prices on the internals, well, i suppose if it were a track racing engine the prices make sense, but not for a street toy. I am guessing a marine crank and a fiero store cam with a sbc head would be enough to make a KRP SD engine a pretty potent 4 banger for the Fiero.

[This message has been edited by Roland (edited 06-05-2005).]

Here are some comparison pictures I put to gether last year when I was rebuilding my Iron Duke. Notice the difference in thickness betwen the piston walls and the outer edges of the block.
The Iron Duke is on the left and the Super Duty on the right.

This is a bottom view comparison. In this case the SD is on the left. The difference doesn't sem as marked but still there.

------------------

quote Originally posted by Roland: well, i guess it is as hopeless a block for mods as most say it is. I guess there are more differences to the SD block than meet the eye upon initial glancing. It's just that when i first looked over a SD block i saw no major differences to the stock block, yet the SD has been known to handle 400+ hp. I suppose the best alternative would be to cough up $2,500 and buy a KRP Super Duty 2.5 block. I dont care much for their prices on the internals, well, i suppose if it were a track racing engine the prices make sense, but not for a street toy. I am guessing a marine crank and a fiero store cam with a sbc head would be enough to make a KRP SD engine a pretty potent 4 banger for the Fiero.

For any Fiero application, a KRP block would be extreme overkill. It's good if you're looking to make over 1000 hp, though. Get on some midget and dirt track classified sites, and try to find a used SD block. That's your best bet.

As far as the differences go, one of the best ways to see this is in the pic above. Look right below the cylinders. The reason that this block is so much stronger, is that the difference in distance from cylinder to the slanted block wall is made up from solid metal on the SD. Not to mention it has 5 cam journals with roller needle bearings. I'll try to get some good shots of key differences when I pull my motor out of its bag.

[This message has been edited by FastIndyFiero (edited 06-05-2005).]

You can build up the L4 but as many have noted, it's not very cost effective. For about the same money you can put in one of the V6 setups and there are a couple besides the 2,8 that pretty much drop in with the 2.8 wiring harness and mounting hardware.

I think there are some other L4 engines that also drop in fairly easy but I don't remember much about that.

That said... There are things you can do to get more power from the OE L4 in many cases. Simple things like making sure the gas pedal is opening the throttle body to WOT can make a huge difference. (See the related article in my cave) If you are 20-30% below WOT with the pedal on the floor that is going to have a gigantic negative impact on performance. I would bet that allot of people bashing the L4 have never actually driven a car with one that is running right and reaching WOT.

A good tuneup and so on will also help release all the availably power from any given engine. Advancing the base timing on a distributor motor sometimes helps but it can hurt if you don't get it quite right.

The point is there are a number of simple things that will rob power from an engine. When you already have a fairly low power engine, these simple things can mean vast cuts in performance.

Along the same line...

If you have an automatic trans... making sure that A it is working/adjusted right and B installing a Transgo shift kit can also help. Allot of people pan automatics but the fact is that the TC multiplier effect can deliver more torque to the input shaft and ultimately the axle than a similarly geared manual can ever hope for. Even at a very conservative 1.3:1 multiply the 134-135 FP (At Crank) becomes 174 FP on the trans input shaft. (More than the 2.8 V6 makes at the crank.) At 1.5:1 you break 200FP on the input shaft. The TC multiply is up to around 1.9-2:1 peak. This is why it is critical to have a TC that is both properly matched to the car and in good working order. A TC that is just a little out of sorts is a large problem.

Usually the first thing to go when someone tries to build up a Duke are the rod and main bearings. There's not enough strength in the crank and block to keep the rotating assembly straight at higher then stock output levels, leading to uneven loading on the bearings and rapid bearing failure.

There is a little room for improvement; people have built up Dukes to produce over 100 HP - but any that I know of that went past 120 HP didn't last very long.

As others have mentioned, to overcome this fundamental weakness in the Duke means changing the block, crank, etc. to Super Duty (or equivalent) parts. Very expensive way to go; you'd get more horespower for less money by swapping in a different engine.