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