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exhaust manifold restrictions by fierofrenzy
Started on: 06-02-2018 06:53 AM
Replies: 14 (326 views)
Last post by: qwikgta on 06-12-2018 10:37 PM
fierofrenzy
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Report this Post06-02-2018 06:53 AM Click Here to See the Profile for fierofrenzyClick Here to Email fierofrenzySend a Private Message to fierofrenzyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm sure someone can tell me if the stock 4 cyl exhaust manifold has those nasty restrictions that the V6 has. I ported my V6 manifolds on my Formula and had the welds strengthened. A definite flow improvement . Now that I own an 87 4 cyl. I'm curious to know if the stock manifolds have those same internal restrictions. If so, I plan on doing the same process to eliminate them.
I ran a search on this and nothing came up. Thx......
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Dennis LaGrua
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Report this Post06-02-2018 08:52 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
I was reported here that the Duke with a non-restrictive header exhaust system experienced a significant power increase. Owner even claimed that he kept up with V6 Fieros. I believe that there is still a source for Duke headers but we have not heard about the source in quite a while.
Check this site out: Iron Duke Performance
------------------
" 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 "

[This message has been edited by Dennis LaGrua (edited 06-02-2018).]

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Patrick
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Report this Post06-02-2018 09:59 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofrenzy:

I'm curious to know if the stock manifolds have those same internal restrictions.


I don't believe anything anywhere has the same stupid inexcusable restrictions as factory Fiero 2.8 exhaust manifolds.

[This message has been edited by Patrick (edited 06-02-2018).]

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theogre
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Report this Post06-03-2018 04:34 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
"I'm curious to know if the stock manifolds have those same internal restrictions."
No and don't bother to charge it.

Most dukes have same crap exhaust manifold from factory. Not just Fiero. FWD cars too. Maybe some trucks too. (88 Fiero tried changing the down pipe and added a hanger but often didn't help much.)
Worse problems when...
idiots "fix" exhaust system and leave out parts and let exhaust pipes etc to move more.
don't fix dogbone engine trans mounts allowing engine movement. More so w/ AT mono mount for 87-88 Fiero and others. See my Cave, Torque Strut

Very Likely has crack now and needs replacement and most use ones are junk too. Dorman and others have new ones.
Crack(s) where
small tube(s) go into center
O2 bung weld
center can crack or even break completely.

What more power then make sure TBI reaches WOT when pedal is floored. Most can't for a number of reasons often even after engine swaps.
See my Cave, Throttle Cable

------------------
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.
(Jurassic Park)


The Ogre's Fiero Cave

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fierofrenzy
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Report this Post06-03-2018 10:11 AM Click Here to See the Profile for fierofrenzyClick Here to Email fierofrenzySend a Private Message to fierofrenzyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, the stock V6 exhaust manifolds have a terrible restriction. An easy honing fix though, once you get the manifold off. ( haha, not so easy, window side that is ).
Theres a header for sale on ebay, but I question weather on not its worth it. I also remember how one member on here stated that the header he had installed repeatedly toasted his starter motors. I don't need that issue.

So once again, are there bad restrictions inside the 4 cyl manifold? It appears easy enough to remove.
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theogre
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Report this Post06-03-2018 11:33 AM Click Here to See the Profile for theogreClick Here to visit theogre's HomePageSend a Private Message to theogreEdit/Delete MessageReply w/QuoteDirect Link to This Post
"So once again, are there bad restrictions inside the 4 cyl manifold?"
No.

Only "Header" listed @ebay I find is same crap manifold w/ chrome and not worth paying $200+.
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Blacktree
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Report this Post06-03-2018 11:37 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
I don't think the Duke exhaust manifold is as restrictive as the V6 ones. That said, I'm sure it could still benefit from headers. Hooker used to make a long-tube header for the Duke back in the day, not sure if they still do.

Can you provide a link to the eBay auction?

[This message has been edited by Blacktree (edited 06-04-2018).]

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fierofrenzy
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Report this Post06-03-2018 07:09 PM Click Here to See the Profile for fierofrenzyClick Here to Email fierofrenzySend a Private Message to fierofrenzyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Blacktree, gee, sorry but I don't know how to transfer a link from ebay on to here. I'm not much of a computer guy at all. if you go onto ebay, and run a search for Fiero, you'll see it listed within a few pages in. Is a chrome piece and I think the manufacturer was OHM, something like that. the last I saw of it the seller was asking $150 for it.
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fierofrenzy
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Report this Post06-03-2018 07:13 PM Click Here to See the Profile for fierofrenzyClick Here to Email fierofrenzySend a Private Message to fierofrenzyEdit/Delete MessageReply w/QuoteDirect Link to This Post

fierofrenzy

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CORRECTION : just go to ebay and enter in Fiero header, it will pop right up. The manufacturer is OBX. I hope this will help.
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Patrick
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Report this Post06-03-2018 07:19 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofrenzy:

Is a chrome piece and I think the manufacturer was OHM, something like that...


Close, but no cigar.



eBay item number: 172685704953

[This message has been edited by Patrick (edited 06-03-2018).]

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Blacktree
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Report this Post06-04-2018 11:07 AM Click Here to See the Profile for BlacktreeClick Here to visit Blacktree's HomePageClick Here to Email BlacktreeSend a Private Message to BlacktreeEdit/Delete MessageReply w/QuoteDirect Link to This Post
That's more like a stock manifold than a header. I doubt you'll get any noticeable power increase.
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WKDFIRO
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Report this Post06-04-2018 11:30 AM Click Here to See the Profile for WKDFIROClick Here to Email WKDFIROSend a Private Message to WKDFIROEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had the 87 5spd coupe with the Hooker Tri-Y and yes it curved right on top of the solenoid and toasted it no matter what kind of Shield I put on. That being said, flow was so improved it blew a hole in my stock muffler after the second day. I used to have a picture of the two exhausts. The Hooker made the stock look like a bad high school welding project.

The responsiveness of the Iron Duke opened up big time and I loved til the car was totaled being rear ended by a pickup truck and pushed Ander the one in front of me.
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Raydar
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Report this Post06-04-2018 01:29 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I had the Hooker Tri-Y on my SD car.
Thermal coating helped tremendously.
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Dennis LaGrua
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Report this Post06-08-2018 11:08 AM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Here's a guy that claims 230HP from a Duke and its not an SD4. Highly unlikely but its sounds tough

230 HP Duke Engine

------------------
" 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 "

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qwikgta
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Report this Post06-12-2018 10:37 PM Click Here to See the Profile for qwikgtaClick Here to Email qwikgtaSend a Private Message to qwikgtaEdit/Delete MessageReply w/QuoteDirect Link to This Post
When my 88 had a 2.5L in it, I installed a aftermarket header w/ open exhaust (no cat) and a supertrapp muffler. Not sure if it was faster, but the engine could breath so much better. It didn't take as long to rev up when I pressed the throttle. RPM's would climb faster with the same amount of peddle effort. If I ever had to have another 2.5L motor in a Fiero, it would get a header and exhaust work before I did anything else.

Rob

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88 Coupe, CJB #95, LS376, F40 and a GT clip
88 GT "Daily Driver" w/ SIII 3800 NA

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