So, i'm thinking about sticking with the duke. Making it look good and show quality. (stock look). If i were to do this i would rebuild the engine with fiero store parts. Making it look show quality by powder coating everything. paint the engine bay a glossy black. Like i said i would rebuild the duke with fiero store parts. Performance cam, their aluminum timing gear set, new push rods and rocker arms. Speed pro pistons with their rings. All new bearings. Hi volume oil pump. I would like to have be running at 100hp! Yes! thats my goal, 100hp! lol, you guys never herd that have you? Its just i'm 16 and i think it would be a good project. I've all ready done the head. The heads new so the top end is already done. I'm sure i could port out the head some. to give it more flow.
I'm 16 and have (hopefully) 80 more years to do a big performance swap! With being a sophomore in high school and a par time job at a sanfrancisco oven. I just don't have the time, money or knowledge to do a 3800 or 4.9 swap. And i kinda like the duke. making it look super nice would be kinda cool. And hey, i like the gas mileage also.
So what do you think? Should i do it. This will come after i do the exterior. I'm transforming my car into a 84 fastback GT.
Any tips, ideas or suggestions would be awesome.
Brian Maxwell
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04:22 PM
PFF
System Bot
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
fiero Specific Speed pro pistons are probobly expensive chevy 305 pistons dont take much bore to fit its only like a 1/2 cubic inch per cylinder over bore and allot cheaper with allot more options. Or if you wanted to stay pontiac and stay on the cheap side of things dont buy fiero 2.5 engine components buy pontiac 301components they are the same thing but ussually cheaper. Also 84 was a bad year make shure you get the exhaust manifold oil gaurd off of a later year fiero it helps prevent fires. edited because I cannot spell after getting off work at 7 and not being a sleep yet
[This message has been edited by Ace McCloud (edited 09-20-2007).]
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04:36 PM
pswayne Member
Posts: 1282 From: Lawrenceville, GA USA Registered: Sep 2006
I know this may seam stupid. But, could i get higher compression pistons and get a little more power? And even if i dont get any power. Would higher compression be better? And for the 301 parts. Do you know of a website of parts? Or a car that had the engine. so i could search and figure out what i can get. And with the beefier pistons, could i get beefier piston rods? I'm not looking into building up the duke for high hp. But making it stronger couldn't hurt.
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04:46 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
Rebuilding a 2.5 can be a rewarding experience for someone who is just getting their hands dirty, automotive-speaking. I fully support you in your mission, but with some caveats.
1) Start with a 1985-1986 engine. They utilize a roller cam. 2) Don't get the Fiero store cam. Get a mild performance regrind of the stock roller cam. Isky cams in CA can do this for about $120. Roller lifters can be reused as well. 3) Don't go with a HV oil pump. It is unnecessary for a near stock engine, it will only eat horsepower and put extra wear on the oil pump drive gear, causing a failure in the area. It happens often with Dukes. 4) Use a crank and rods from an 87 or newer 2.5 Iron Duke (doesn't have to be a Fiero one) The later rods are stronger, as well as the later crank, which fits just fine even though it looks a little different
Don't use 305 Chevy pistons. They won't fit. They are for a bore of 3.736" whereas stock Iron Duke is 4.0" (101.6mm)
I have been elbow deep in my fair share of 2.5 overhauls, so if you need any other advice, PM me.
Good Luck! Kurt
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04:48 PM
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
Don't use 305 Chevy pistons. They won't fit. They are for a bore of 3.736" whereas stock Iron Duke is 4.0" (101.6mm)
Kurt
The Duke is not a half a 301 ummmmm not everything you hear on the forum is ture I guess Note: nobody disagreed with the exhaust manifold oil gaurd comment I guess I finally got something right PS If you want a 85 duke or any parts off of one I just pulled a working one this week. PM me if interested its gonna sit around for years if not
[This message has been edited by Ace McCloud (edited 09-20-2007).]
so, i will want to get a 85-87 2.5? because of the roller cam? and 87 parts because there stronger? (rods) Will my 84 head fit on the block? So i could use my intake and exhaust manifolds???
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04:55 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
Being half a 301 is mostly true. They share rod bearing shells, con rod lengths and bore and stroke.
That being said, the blocks and cranks are obviously not interchangeable, and neither are the heads, though 301 heads are actually worse than Iron Duke heads. There isn't much useful you can get out of a 301. I was looking at scoring some 301 turbo pistons, but they have an odd dish in them designed to work with the much different combustion chambers of the 301 heads.
From what I can remember, you can use Chevy 350 TBI pistons for a compression bump up to the neighborhood of 9.4:1 though. Their compression height, pin diameter, and dish volume are I think just about all right for the Duke.
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04:59 PM
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
so, i will want to get a 85-87 2.5? because of the roller cam? and 87 parts because there stronger? (rods) Will my 84 head fit on the block? So i could use my intake and exhaust manifolds???
HE said 85 to 86 2.5 you were right about the 87 parts though. Heads should fit all years I think 88 was weird though.
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05:00 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
so, i will want to get a 85-87 2.5? because of the roller cam? and 87 parts because there stronger? (rods) Will my 84 head fit on the block? So i could use my intake and exhaust manifolds???
You will want an 85-86 engine block, lifters, and cam because after that the Duke went to DIS ignition, which is not compatible with your car's ECM.
The 84 head you have already had redone will bolt right on, and 85-86 manifolds are the same and use the same gaskets as the 84s.
87+ parts as far as rods and cranks are the best. Somebody with spare Dukes lying should really take some pics to illustrate the difference in beefiness between 84-86 connecting rods and the later ones. I forget the casting numbers, one is like 684 and the other is like 317.
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05:03 PM
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
people use 350 pistons in performance duke builds on here allot. This next comment is not entended to start a war and if it does I am sorry in advance but you could easily slap a carb on a 2.5. TBI was odd ball and wasnt made for all that long and you cannot tune it with a screwdriver
With a carb, could i get better gas mileage? And all i really would have to do is connect gas lines and throttle cable, couple vacuum hoses.???? I would have to make an adapter plate to my intake but if i could get better gas mileage, minus wiring issues.. tune in myself. i think it would be a good ideah?
Allright. i just searched and found allot of info on 2.5 with carb. Its def to much for me. Theres to much to do and i don't think i could do it. Thou it looks cool and everything i dont think its for me. I think i'll fab up my own intake when the time comes. A cold air using aluminum piping going to the side scoop. a shiny cold air intake will make the engine bay look allot nicer also.
Thanks for your posts!
Brian Maxwell
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06:11 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
A member here has a properly sized and jetted carbed duke that was doing 65mpg with no emissions controls. Porting up the heads would help with some flow, and if you can run a dremel you can probably pull it off.
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06:47 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
A member here has a properly sized and jetted carbed duke that was doing 65mpg with no emissions controls. Porting up the heads would help with some flow, and if you can run a dremel you can probably pull it off.
Thats pretty amazing. Just imagine the mileage gains if Prius and Insight owners switched their cars over to carbs! With numbers like that I should swap my Silverado over from F.I. to carbed so I can go from 16 to 34 mpg! It must be a big conspiracy theory with all the worlds automakers to ruin our MPG with feedback fuel controls...uh...right.
An air die grinder with a carbide burr and a couple stones and some sand rolls would be a lot more appropriate for porting. A dremel is a toy, and can't really remove much material. This is not to mention that Dremel accessories don't optionally come with long shanks, so you can't get to most of where you need to go when working deep on the short side radius.
[This message has been edited by KurtAKX (edited 09-20-2007).]
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08:46 PM
Mr.PBody Member
Posts: 3172 From: Cincinnati, Ohio, USA Registered: Oct 2006
Yeah but the principal is the same, and if you can't afford a proper grinder the dremel will work. Hes a member here and he got 65mpg, he built it up entirely for MPG reasons, different from what BMAX wants but he asked if a carb can add mpg. Somewhere here proved in the case of the duke, it is possible. TBI really isn't that effecient and a carb is easier to tune. Todays multi port EFI and direct injection are totally different.
And what compression will i want? i want to run higher compression, i could get a little more power out of it. And aluminum pistons would be cool. Any help would be appreciated, Whats the pin size of the stock pistons?
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09:49 PM
PFF
System Bot
Dennis LaGrua Member
Posts: 15880 From: Hillsborough, NJ U.S.A. Registered: May 2000
Before you get going on a 2.5L rebuild, price all the parts and machinework necessary, then add 25% over for the things that will come up. Next go out and price a longblock. I'll bet that the longblock comes out the better buy.
------------------ 87GT 3.4 Turbo- 0-60 5.2 seconds 2006 3800SC Series III swap in progress Engine Controls, PCM goodies, re-programming & odd electronics stuff " I'M ON THE LOOSE WITHOUT THE JUICE "
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11:06 PM
Mr.PBody Member
Posts: 3172 From: Cincinnati, Ohio, USA Registered: Oct 2006
Wait I thinkwe finally got something on those EFI people who Like to gang up on people and attack them The only car I am fimilliar with that I know this was also true is the chevy sprint it went carb to TBI and the milage dropped.
quote
Originally posted by KurtAKX:
Wiring is identical between 84-86 engines. Just use your old sensors.
Carb will not get you better mileage, sorry. It will cost you money, time, and frustration.
Duh, You mean if you change parts from origanal to different they would require money, time, and frustration well a different year engine is out 350 pistons are out any work changing to differnt parts are out
Hold on with the EFI war the only reason I brought up the carb at all is because if you put too much power into the duke the factory TBI wont be able to keep up and if you tried to swich to a multi-barrel TBI seup you would have to fab an intake and do wireing but an intake off an earlier 2.5 like the chevy citation inake and carb I used should fit without to much work. I just mean that their are not allot of TBI preformance parts out there.
The 350 pistons i found dont need any work..I dont think.
Here is what i want to do. Get a 85 or 86 2.5. Together. Not in pieces. I want to rebuild the duke so it is running great, So it can be really reliable and take me anywhere when needed. I want it to have a better cam. and the strongest parts i can get without doing anything crazy and keep the price low.
The long block is a good idea. But that already comes with the parts I'm going to replace. and I'll learn more by rebuilding the whole engine.
For my fastback conversion.. Do any of you know if the wire harness for the tail lights (the one i'm getting with the gt stuff) will plug in or work with my car? 84 auto.
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10:55 AM
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
Originally posted by bmaxbox: Here is what i want to do. Get a 85 or 86 2.5. Together. Not in pieces.
I have a complete 85 duke I just pulled from an 85 coupe I had laying around it ran fine and is complete I am willing to let it go for allmost no $ PM me if you are interested. Good luck
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11:22 AM
fierodeletre Member
Posts: 834 From: Behind Animal's Drum Set. Registered: Oct 2006
I would strenuously suggest trying to get an 86 block over an 85, Not all 85s had the roller cam. I did not know that the 87-88 crank and rods would fit in a 84-86 block. That's kind of cool.
------------------ If you can't be good, be good at it.
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11:44 AM
Ace McCloud Member
Posts: 167 From: Marble Hill, Missouri, United States Registered: Jul 2007
All 85 engines are roller. I have yet to have somebody show me one that isn't. The easy way to tell if the engine has a roller cam (especially out of the car) is to look at the lifter cover. There was a small change to the casting to accomodate the lifter guides that keep the roller lifters from rotating, and when this change was made, the cover received a minor change. "Flat tappet" engines have a roughly rectangular cover, whereas the roller engines have angled in corners on the bottom. See crude MS paint image.
The engine block currently in my car started its life in a 1985 Pontiac 6000. From what I have read some very late 84 Fieros got rollers, and by 85 all the car lines with the Iron Duke had them.
[This message has been edited by KurtAKX (edited 09-21-2007).]
after work i'll have some more questions i'm sure. But for now, I really like the 350 pistons. I'm going to need flat top with two valve reliefs? I'm guessing. what about the compression distance? Any help with this would be appreciated. I'm sure the 350 pistons are made stronger and will be a nice add on to my engine.
[This message has been edited by bmaxbox (edited 09-21-2007).]
I just researched a bunch and have more questions. I still need to know about the pistons. compression distance? pin diameter? valve reliefs?
I saw some where about adding a after market ignition coil. I saw the ones for 87 and 88 on fierostore. But what about the ones from msd. like this one.. http://store.summitracing.c...813+115&autoview=sku
I'm sure a good ignition will be a must if i want it to be reliable.
I'm researching about roller rockers. If i want them i will need 1.75:1, what stud size is mine? And will i need to do somthing with my rods? get longer ones or do anything like that?
I just now saw that by switching over to the 85-86 block i will be converting to DIS. Can some one explain this to me? and i already know i will have to get the ecm for that engine*.
On fierostore theres a distributer for the 84 and another for the 85-86. I thought DIS meant it didn't use a distributer? I thought the ecm controls the timing. hmmm. I didn't even think there was a hole for a distributer. But it shows a gear on the end of it. (fierostore)
[This message has been edited by bmaxbox (edited 09-22-2007).]
84-86 engines are interchangeable for the most part. Putting an 87+up engine into an earlier car is at least as much work as swapping a V6 would be. There are allot of electrical changes to go with the mechanical differences.
Rebuilding... Be certain what year engine you really have. Many 84-85 cars got engines replaced due to warranty/recall work. The later engines have roller cam sets from the factory and that will affect what you do during rebuild. The roller cam engines apparently have different oiling hole setup for the lifters. (The roller lifters are taller.)
If you're just replacing it... always look for the roller cam engines.
------------------ 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)
So far i have pretty much decided on. Roller cam engine 85 or 86. 350 pistons. flat top two valve reliefs? is this right?http://store.summitracing.com/partdetail.asp?part=STL%2DH631CP&autoview=sku 87 rods. ported head. MSD ignition aluminum timing gears Performance cam. fiero store or having mine machined? New oil pump? All new bearings.
I want roller rockers if possible.
New exhaust manifold. and exhaust wrap.(my exhaust is already done with a catco cat and a thrush muffler from summit.
TBI will be rebuild. the intake will be hot tanked and cleaned out. And powder coated.
everything will be cleaned. Probably hot tanked. and powder coated or high temp paint.
Whats the piston rod length for the this engine? do any other rods fit? I saw something about H beam and sbc rods. I'm not sure.
The heat stuff on the firewalls will be taken off. All walls will be painted glossy black. Tin-foil type stuff will be put on the fire wall by the seats. All brackets will be painted.
And I'm thinking about moving the battery to the front. To make the engine bay more open.
And can i take the cruise control out? i don't use it and will never use it. All it is, is a waste of space for me. I have a vacuum gauge that will take place of the vacuum hose on the intake. I'll be able to start all this after i do the fastback swap. swap will be in about 4 weeks. (Lets hope) After that i will probably have to wate another two weeks for paint. So about 2 months i can start this. maybe i can build the engine over winter? On a cradle and do a straight swap.
Anything else you can think of that will make my car really reliable would be helpfully.
I have full roller rockers on my duke. You have to use two value cover gaskets or the rockers will hit the cover. Remember to use good gaskets with sealer and don't over tighten.
