I've been on this trail of trying to increase HP on the Duke engine. One of the sites that has pointed the way is Ira Crummy's Duke Site. He put a lot of good work into it and there is a lot of good information to be found. I do have a criticism and that is that Ira indicates virtually everything OTHER than the simple task that will open up the Duke and increase HP. This one thing is removing excess casting material immediately before and after the intake valve. One can also increase valve size to 1 7/8" but that is more involved and costly. For these tasks look to Dave Vizard's book on How to Port and Flow Test Cylinder Heads. This single thing is by far the most important and effective thing a Duke owner can do to increase HP and it is virtually free. Now, there are a lot of lazy armchair naysayers types that will tell you it is too expensive, your car will explode and all sorts of unsubstantiated B.S.. I have often wondered what motivation these folks have that compels them to foam at the mouth in this way. These folks seem to assume all Duke owners want to bring there Fiero to Drag festivals and compete for 1/4 mile times. Which is silly. So if you have a Duke and want to get the motor up in HP to somewhat complement the looks of the car than get out your grinder burrs. Check out my THREAD to get you started.
How are you testing the modifications to ensure that flow is equal across all cylinders after you grind? Proper flow testing is not cheap or free.
Why not mill the head to help bump the compression, and advance timing and switch to higher octane fuel at the same time?
It is indeed something which can become very expensive very quickly, for people who don't have the skills to do the task right. Even for those that do, if the necessary tools aren't all readily available, acquiring those tools can be costly.
Sure, it's a simple way to help the poor Duke out with a little more power, if done right, but virtually free is not a particularly apt description of it. It's misleading. This isn't a general solution for people who want more power in their Fiero, but it is a fine solution for those who want to keep the original engine and desire a bit more power.
But as far as unsubstantiated BS goes, do you happen to have any flow bench numbers for all ports, before and after, your work? Or before/after dyno charts for your car? You've claimed a roughly 30% increase in power over stock with your changes. Would be nice to see evidence of that other than your seat of the pants guess.
How are you testing the modifications to ensure that flow is equal across all cylinders after you grind? Proper flow testing is not cheap or free.
Why not mill the head to help bump the compression, and advance timing and switch to higher octane fuel at the same time?
It is indeed something which can become very expensive very quickly, for people who don't have the skills to do the task right. Even for those that do, if the necessary tools aren't all readily available, acquiring those tools can be costly.
Sure, it's a simple way to help the poor Duke out with a little more power, if done right, but virtually free is not a particularly apt description of it. It's misleading. This isn't a general solution for people who want more power in their Fiero, but it is a fine solution for those who want to keep the original engine and desire a bit more power.
But as far as unsubstantiated BS goes, do you happen to have any flow bench numbers for all ports, before and after, your work? Or before/after dyno charts for your car? You've claimed a roughly 30% increase in power over stock with your changes. Would be nice to see evidence of that other than your seat of the pants guess.
Hey Dobey, I did not bother to perform any flow testing on my head and do not feel it is even helpful. Flow numbers dont really mean squat. What is proof is 0-60 times. I know this thing is quicker but I have not done a 0-60 timing either. Why not? Because I dont care what the precise numbers are. All I care about is that my engine gets the car up to speed at a rate that is not embarrassing. Before I was embarrassed, now this thing kinda rocks. I understand your approach but I question you whether or not these numbers actually result in a better seat of the pants ride man. It's all about the ride and not at all about the numbers for your typical Fiero driver.
And Dobey there is no reason to be concerned with exact flow equality between the cylinders. If one is reasonably consistent about what and how much they take out then their result will be reasonably consistent from port to port and that is as accurate as is needed. The equipment I used was a 3000 rpm electric drill and a 5/16" carbide flame shaped bit. So were talking 10 bucks if you own a high speed drill. Regarding skills...well one learns by doing. There is really no other way is there. With Vizards book as a guide anyone with an IQ of 90+ can pick it up on the fly. So get those Dukes rolling!!
DUKE DUKE DUKE DUKE of oil DUKE DUKE DUKE of oil DUKE DUKE DUKE of oil
YaY! I found out what the bottle neck actually is on the Duke! The intake valve. Fellow Dukesters, the intake valve and it's immediate adjacent areas is where to concentrate your efforts! YEEHAA!
DUKE DUKE DUKE DUKE of oil DUKE DUKE DUKE of oil DUKE DUKE DUKE of oil
YaY! I found out what the bottle neck actually is on the Duke! The intake valve. Fellow Dukesters, the intake valve and it's immediate adjacent areas is where to concentrate your efforts! YEEHAA!
Do a search of TopNotch's threads. He made some seriously meaningful mods to an 88 Duke. One of the mods was (I think) the replacement of the head with an S10 piece. He hasn't dynoed his, either, but he said that you can absolutely feel the difference from stock.
------------------ Raydar 88 Formula IMSA Fastback. 4.9, NVG T550 Praise the Lowered!
Do a search of TopNotch's threads. He made some seriously meaningful mods to an 88 Duke. One of the mods was (I think) the replacement of the head with an S10 piece. He hasn't dynoed his, either, but he said that you can absolutely feel the difference from stock.
Interesting, this head had the right # but the a couple of the bolt holes were repositioned. Also the water spout was on the wrong side. I still dont know what this head was from originally.
Interesting, this head had the right # but the a couple of the bolt holes were repositioned. Also the water spout was on the wrong side. I still dont know what this head was from originally.
IIRC,the Duke engine was used on S-10's (stronger version), Pontiac 6000, Olds Cutlass Ciera and Chevy Celebrity. AMC also used it on Jeeps for a short while. Its a common engine and the one in the Fiero seems to be the light duty version. A quick way to a few more horses would be to improve the exhaust, go with a larger throttle body and port a bit as White84se has done. I would not spend a ton of money on this engine as you hit the threshold of diminishing returns rather quickly but I have seen Duke builds with cams, high compression SBC pistons, MSD ignitons , larger throttle bodies and headers. Neil and Dawn Kline (racincouple) did such a heavy mod performance build on their Duke maybe 10-12 years ago and they reported that the performance was good. Due to health issues Neil left the Fiero hobby long ago , his car was sold and is still out there somewhere in an enthusiasts collection. .
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
...the simple task that will open up the Duke and increase HP. This one thing is removing excess casting material immediately before and after the intake valve. One can also increase valve size to 1 7/8" but that is more involved and costly. For these tasks look to Dave Vizard's book on How to Port and Flow Test Cylinder Heads. This single thing is by far the most important and effective thing a Duke owner can do to increase HP and it is virtually free.
quote
Originally posted by White84SE:
Agreed. The Paul Vanderley designed SD4 heads out of the box (before any porting) flow 88% more than a stock Duke head! Here's my SD4 head. The Stainless Steel intake valves are 2.055" diameter and the exhaust valves are 1.600" in diameter. Other than a good flowing head, the engine also needs a camshaft with a grind that produces power in the range you want.
