whatever you do to the duke, get pictures, take notes and do a write-up so the rest of us will have something to read during the garage season

the actual rockers on the iron duke come from stovebolt I6's, you can get roller rockers at 1.75(compcams 1033-12)

personally i think the duke could use some oil control, baffling and such.

quote Originally posted by baldlobo: i don't know but it was kurt who did that flowbench; yup got to love the cliff that block flow(short side goes out the open part of the valve area, and the long side hit's the wall).

Yep KurtAxx had an interesting DIY flowbench going. I am just gonna use my built in "seat in the pants" flowbench. Most of these little tweaks are very conservative and well proven and I am not gonna try to convince anyone anyway. The Singh Grooves just make simple sense to IMO although it is disputed by some and embraced by other industry experts.. But yep I will post pics as I go this fall. For me the telling test will be 0-60 times and gas mileage. As a matter of fact the flowbench will not test compression expansion events as far as I know.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

When I did mine I just dressed up the swirl structures to where it just looked like they would flow better:



The intake manifold was hogged out for the Holly big bore TBI:



Crane roller rockers:



Accelerated motion mild cam, aluminum timing gear, Hooker headers:





A lot of work for 125 HP but it had to be rebuilt anyway. 1986 Engine

Wow yea looks like you did a full work up! Hooker headers aye? Looks like you blended those valve seats nicely. I figure those guide bosses can be skinnied and I am gonna try a Singh Groove along that flat triangular area in the chamber. Shoot some fuel to that "corner" of the chamber. Did you drive it prior and after? What is your impression?

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

.. Getting to be an interesting post..I love the blue block..
..I am going to write up a head modification post that will help you & others ,,I have to take my time on this because my brain has been scrambled ,these tips will be a compilation of my own experience,rebuilders ,plagerizing hot rod/performance magazines magazine ..It should have wide appeal to all forum members with gas engines.I will post this saturday morning
..The first tip will be the 3 angle valve job....Simple but ignored,,ya gotta let loose a few dinerio/sheckles for the tire smoking Flying duke 8 second 0 to 60
..performance is in the head modification

I went with Red for my rebuild. I kept the stock rockers....less friction drag with the rollers right? Same cam basically...mild street (Fiero Store). Got a new fuel pump and adjusted fuel pressure up to 14LBs worked to wake the Duke. Anyway for what it is worth I feel it gets a good 15-20 more than before. I figure it was dragging a bit so perhaps 90HP after I figure it feels like 110-115. I had a Toyota Celica with 118 and just a little lighter before and this feels like it is quicker in general but that may have to do with gearing and lower center of gravity etc. I will be surprised if this porting squeezes much more out but it's nearly free so why not?

I'd say the big improvements have come from the new cam and new fuel pump mostly. Oh and for sure that stock catalytic converter had to go.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

anyone?
https://www.fiero.nl/forum/Forum4/HTML/053905.html

quote Originally posted by White 84 SE: Wow yea looks like you did a full work up! Hooker headers aye? Looks like you blended those valve seats nicely. I figure those guide bosses can be skinnied and I am gonna try a Singh Groove along that flat triangular area in the chamber. Shoot some fuel to that "corner" of the chamber. Did you drive it prior and after? What is your impression?

Not sure if thinning the bosses will do much. The fuel and air is going to go outward from there. As another has said, a three angle valve job is more important. (I did not do that but should have). I had heard of some totally hogging out the ports eliminating the swirl structure. But it seemed to me, the whole design of the head centered around swirling the fuel air into the chamber and you can see that from the design of the port and the upper combustion chamber. Not sure if the "Singh Groove" would help the swirl or interfere with it. The head is kind of a crappy design with the number 2 and 3 exhaust ports being connected and the integrated EGR passageway.

I would say the cam (Accelerated Motion) with the gasket matching and porting was the most bang for the buck. In my opinion, the lower RPMs I run to try and keep it from killing itself means you dont really need the Holly Big Bore and the Headers. I did also balance the engine, even the flex plate bolts to try and help that situation.

I drove it before and after. Using the weight and 0-60 times it comes in between 120 to 130 HP on stock electronics. My impression is that it has a little more power in the 2-4k rpm range. Its modified stock. So it keeps that stock all it can be kind of thing. But, in a straight line you'll get creamed by ricers and pick up trucks who will be constantly wanting to race you.

quote Originally posted by fst4rsc: Not sure if thinning the bosses will do much. The fuel and air is going to go outward from there. As another has said, a three angle valve job is more important. (I did not do that but should have). I had heard of some totally hogging out the ports eliminating the swirl structure. But it seemed to me, the whole design of the head centered around swirling the fuel air into the chamber and you can see that from the design of the port and the upper combustion chamber. Not sure if the "Singh Groove" would help the swirl or interfere with it. The head is kind of a crappy design with the number 2 and 3 exhaust ports being connected and the integrated EGR passageway. I would say the cam (Accelerated Motion) with the gasket matching and porting was the most bang for the buck. In my opinion, the lower RPMs I run to try and keep it from killing itself means you dont really need the Holly Big Bore and the Headers. I did also balance the engine, even the flex plate bolts to try and help that situation. I drove it before and after. Using the weight and 0-60 times it comes in between 120 to 130 HP on stock electronics. My impression is that it has a little more power in the 2-4k rpm range. Its modified stock. So it keeps that stock all it can be kind of thing. But, in a straight line you'll get creamed by ricers and pick up trucks who will be constantly wanting to race you.

Ya know I think simply doing that port match and the In the A.M. I will pull the head. It has only been 2 years since it was cleaned well and perhaps the dead spots in the chamber might be evident.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

Here's a visualization of why I think a Singh Groove will not interfere with the swirl port design in the Duke head. I am thinking that the swirl port functions only during intake. The fuel (green) is drawn in and downward in a swirling manner as designed and it's function complete. No notches are placed along the swirl directing path to interfere. Compression occurs as usual. The expansion phase is where the Singh Groove (yellow) may have some effect. If it is aligned directly in line with the spark it will collect some rapidly expanding ignited fuel (orange) and direct it toward the far end of the chamber. Without the groove there is a deflection which in effect shelters the far end of the chamber from expanding fuel....to a certain extant.

The theory is that a Singh groove can scavenge fuel that would go unburned and contribute to pollution and use it for power or mileage.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

quote Originally posted by fst4rsc: When I did mine I just dressed up the swirl structures to where it just looked like they would flow better: The intake manifold was hogged out for the Holly big bore TBI: Crane roller rockers: Accelerated motion mild cam, aluminum timing gear, Hooker headers: A lot of work for 125 HP but it had to be rebuilt anyway. 1986 Engine

Wow great engine!

quote Originally posted by White 84 SE: Here's a visualization of why I think a Singh Groove will not interfere with the swirl port design in the Duke head. I am thinking that the swirl port functions only during intake. The fuel (green) is drawn in and downward in a swirling manner as designed and it's function complete. No notches are placed along the swirl directing path to interfere. Compression occurs as usual. The expansion phase is where the Singh Groove (yellow) may have some effect. If it is aligned directly in line with the spark it will collect some rapidly expanding ignited fuel (orange) and direct it toward the far end of the chamber. Without the groove there is a deflection which in effect shelters the far end of the chamber from expanding fuel....to a certain extant. The theory is that a Singh groove can scavenge fuel that would go unburned and contribute to pollution and use it for power or mileage.

Ok I think I see what your saying. A picture is worth a thousand words! I'll have to think about it for awhile to really wrap my head around it. I wonder if it would effect exhaust flow, like trapping stuff..... Maybe that would be good? I suppose the true effect would need to be measured by a dyno or something with no other changes. Interesting. Give it a go. If you dont like it, another head is probably cheap!

Cool, so now I took a look (and feel) of the Duke head and I have an observation..



Check out the valve throat. It is restrictive. Under there is about a 1/2" thick piece of iron where the valve seat has been cut. This "valve throat" are is about a 1/4" more constricted than the actual valve opening. Air/fuel is required to pass this smaller opening before passing the intake valve itself. This restriction may be the Holy Grail for Duke owners.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

...AS others more knowledgeable than I have said ,,the 3 angle valve job is the way to go on the duke,,the area around the valve is where 80% of your gain will come ..
..DO minimal work on entrance wall,s ,, except to port match,,when you port match ,you do not go in more than 1 inch,,a consistent uniform flow ,MEASURE...use templates,use guides,,each port is consistent ,,It is the small things that make a real difference in engines that have no real performance parts available..

..an 84 to 86 duke with 130 horsepower is a firebreathing duke you can not over rev,, this comes from reading this forum and other forums where the duke is discussed,,I have only worked with the duke head to obtain improved Gas milage ..
..If you ever drive an 88 duke 5 speed in good tune,, any one with an 84 to 86 will feel cheated

YA GOTTA GO TO a different crankshaft to really build power ,best to use a different block.. ya gotta work with what you got..

EDIT= do no get carried away around the valve seat ,,on some engines they will pop out or loosen

[This message has been edited by uhlanstan (edited 09-29-2010).]

quote Originally posted by uhlanstan: ...AS others more knowledgeable than I have said ,,the 3 angle valve job is the way to go on the duke,,the area around the valve is where 80% of your gain will come .. ..DO minimal work on entrance wall,s ,, except to port match,,when you port match ,you do not go in more than 1 inch,,a consistent uniform flow ,MEASURE...use templates,use guides,,each port is consistent ,,It is the small things that make a real difference in engines that have no real performance parts available.. ..an 84 to 86 duke with 130 horsepower is a firebreathing duke you can not over rev,, this comes from reading this forum and other forums where the duke is discussed,,I have only worked with the duke head to obtain improved Gas milage .. ..If you ever drive an 88 duke 5 speed in good tune,, any one with an 84 to 86 will feel cheated YA GOTTA GO TO a different crankshaft to really build power ,best to use a different block.. ya gotta work with what you got.. EDIT= do no get carried away around the valve seat ,,on some engines they will pop out or loosen

Thanks Uhls, my valves already have a 3 angle job on them. Now just take a good look at that valve throat. It is a good 3/16" tighter than the valves. That is an obvious bottleneck but perhaps the reason for it is that it may be hard or time consuming to sculpt. I got time but other than just using a diegrinder and trying to be careful I dont know any specialized things about doing it. They are actually contoured toward the center rather than away. It would be cool if there was some tool that would go into the valve guide boss for alignment and could be adjusted to size. A slip in there would be pretty bad.

[This message has been edited by White 84 SE (edited 09-29-2010).]

Oh shoot Dukesters... The more I study the intake port/passage ways the more I realize it's shape is nearly entirely as designed. No obvious production related flaws...although there is plenty of fine tuning to do. I.E. little casting bloopers and some blending to do. That inward slope I refered to above is as designed. Actually I have found that such a horn shape going into the combustion chamber is designed to speed flow so and this has an effect of directing swirl and discouraging back flow. The Duke head seems inherently a swirl port design and hogging it out not to be may or may not help any. Smart money seems to be on refining casting flaws general blending and considering larger intake valves.

Right now I am studying Vizards "Porting School Series" before continueing. Talk at ya later but hopefully I will find stuff to do that will help.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

[This message has been edited by White 84 SE (edited 09-30-2010).]

The light at the end of the tunnel is visible,, the younger a gear head is the more "" bigger is better come into play""
..#1 on the BIG hit list is the cam ,,#2 is the ports
..Have the modifications compliment each other
,,With Girls & the Fiero stock exhaust manifold bigger,wider is better...


Red 86 Fiero GT 4 speed ,V6 lightly modified,custom taco bell smell interior

[This message has been edited by uhlanstan (edited 09-30-2010).]

Have you had a chance to look at older crossflow heads?

quote Originally posted by KurtAKX: Have you had a chance to look at older crossflow heads?

No I have not but these swirlport heads are fairly developed compared to the ordinary sort. Where the regular sort might benefit from raising the floor the Duke swirlport has a staircase. Where one head might benefit from a side leaning passage the Duke has a scroll. Currently I see nothing to do other than blending, the Singh groove and obvious casting flaws. Bummed I thought this was gonna be so much fun and I would find all sorts of easy HP gainers. I suppose in the back of my mind I know of many 2.5L engines that would perform very well in a Fiero yet this one is a bit of a dog. Makes a guy think it might need some easy tweaking etc... I still think the Duke head can get bigger valves but that costs $$. I will contact a couple machine shops and if more than $200.00 including valves I will just keep to the cleanup and Singh grooves only. Apply that cash to an eventual swap perhaps. If I don't go bigger valves I bet it will still have noticeably more power after doing the simple stuff.

Hey Kurt by the way, have you seen Vizard's super cheap flow bench. Costs like $20, just need a spark plug, some plastic tubing, a 1x2x8, some food dye, some clay, a vacuum cleaner......and maybe a few other things... I remember you constructing something some time ago.

Vizard alluded that in some ways he wished he kept to the "old school" flow bench idea because it was simple and was able to tell if a porting or valve improved flow and by what %. That is after all what he was trying to do and all the calibration stuff was just for it's own sake etc.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

[This message has been edited by White 84 SE (edited 10-02-2010).]

quote Originally posted by White 84 SE: No I have not but these swirlport heads are fairly developed compared to the ordinary sort. Where the regular sort might benefit from raising the floor the Duke swirlport has a staircase. Where one head might benefit from a side leaning passage the Duke has a scroll. Currently I see nothing to do other than blending, the Singh groove and obvious casting flaws. Bummed I thought this was gonna be so much fun and I would find all sorts of easy HP gainers. I suppose in the back of my mind I know of many 2.5L engines that would perform very well in a Fiero yet this one is a bit of a dog. Makes a guy think it might need some easy tweaking etc... I still think the Duke head can get bigger valves but that costs $$. I will contact a couple machine shops and if more than $200.00 including valves I will just keep to the cleanup and Singh grooves only. Apply that cash to an eventual swap perhaps. If I don't go bigger valves I bet it will still have noticeably more power after doing the simple stuff. Hey Kurt by the way, have you seen Vizard's super cheap flow bench. Costs like $20, just need a spark plug, some plastic tubing, a 1x2x8, some food dye, some clay, a vacuum cleaner......and maybe a few other things... I remember you constructing something some time ago. Vizard alluded that in some ways he wished he kept to the "old school" flow bench idea because it was simple and was able to tell if a porting or valve improved flow and by what %. That is after all what he was trying to do and all the calibration stuff was just for it's own sake etc.

767 and 373 are the worst flowing of any Duke head... stick with them at your own peril.

quote Originally posted by KurtAKX: 767 and 373 are the worst flowing of any Duke head... stick with them at your own peril.

Thanks Kurt, excuse my lack of knowledge please but which Dukes have these model heads? Thanks!

[This message has been edited by White 84 SE (edited 10-14-2010).]

Have you looked at 702 / 552 heads yet? I really think you should... schedule a Saturday AM to be a go to the JY day, and see for yourself.

They're on lots of pre-84 crossflow Iron Dukes like old CJ jeeps, carbureted Citations, and the like....

I'll see if I can get some pics of one I have on the bench right now, but no promises.

[This message has been edited by KurtAKX (edited 10-14-2010).]

quote Originally posted by KurtAKX: Have you looked at 702 / 552 heads yet? I really think you should... schedule a Saturday AM to be a go to the JY day, and see for yourself. They're on lots of pre-84 crossflow Iron Dukes like old CJ jeeps, carbureted Citations, and the like.... I'll see if I can get some pics of one I have on the bench right now, but no promises.

Thanks a million if you can. Kurt do you know where info on the various Duke heads can be found? So far I have found only info on the various engines themselves.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

I keep getting busy, but I haven't forgotten about you...

Look like a great thread White' 84. Going to my favorites. I just with I had time to read it now. Good luck.

btw, I got my duke running strong over the summer and the car driving like a dream.

-Michael

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"A guy know's he's in love when he loses interest in his car for a few days." -Tim Allen

He who dies with the most toys... still dies.


Check out my restoration!

Yea Fierology, nice work on the restoration. By the way, this thread wont be resolved until spring time. I will have my Fiero in the garage this winter so I am in no hurry. I will probably have a little thread on windshield replacement....other than that all is well.

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

Here's a few pictures. They're far from scientific, I just tossed a 3/8" extension in the port in a few of them so you could get a feel for the size of the ports relative to a familiar object.

767 Casting pics:
http://s892.photobucket.com...ro%20VIN%20R%20pics/
552 Casting pics:
http://s892.photobucket.com...re-84%20iron%20duke/

...didja' head back to the drawing board?

Hey Kurt, that 552 looks a lot like a SD! The other seems like a regular on the surface. What have you found about these heads? Interesting!

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White

quote Originally posted by White 84 SE: Hey Kurt, that 552 looks a lot like a SD! The other seems like a regular on the surface. What have you found about these heads? Interesting!

The ports are like half the size of SD heads, but at least they're not swirl port. They flow more than the swirl heads- how much I can't tell you, because I can't find all the pieces of my flow bench since I moved.

I can tell you the chambers measure out around 52ccs. I think the stock head was something like 45cc, so with this head and no other changes, you'd be knocking yourself down from like 8.9 compression to about 8.25.

I'm getting this one magnafluxed next week, and if its not cracked, its going on my motor, with flat-top pistons, to net an approx 9.8 compression ratio.

quote Originally posted by KurtAKX: The ports are like half the size of SD heads, but at least they're not swirl port. They flow more than the swirl heads- how much I can't tell you, because I can't find all the pieces of my flow bench since I moved. I can tell you the chambers measure out around 52ccs. I think the stock head was something like 45cc, so with this head and no other changes, you'd be knocking yourself down from like 8.9 compression to about 8.25. I'm getting this one magnafluxed next week, and if its not cracked, its going on my motor, with flat-top pistons, to net an approx 9.8 compression ratio.

Sounds awesome keep us posted and good luck on it!!!
By the way, which engines were these on? And how are you increasing the compression? You mentioned flat top pistons...I gather stock is considered concave...?

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84 Duke, Holley TBI, Manual Trans 4.10, CompuCam, White