Northstar Fiero swap, 180* headers, not HMT style
 

I bought a Maroon 88GT that had a 3.4 DOHC swap in it from a guy in Oklahoma a few years ago. I redid the 3.4 swap, drove it for about a year, then sold it to a good friend who drove it for another year or two. Well it developed a few issues, and he ended up blowing the transmission. I found a Getrag in a junkyard for $60, and we managed to find a good deal on a 275hp N* that had just been rebuilt, but never got installed. The N* and Getrag sat around, but my friend came up with the time and money, so we've begun work on the project. For now, the plan is to leave the N* block stock, run it off a 7730 ECU, and I'll be making some trick headers for it (More details in a bit). I would have liked to get a 300hp variant, but this one came up at the right time, for the right price.

In the past few weeks, we got the transmission clearanced for the N* starter, and bolted that up. Today we finished up the cradle modifications, and it goes down to the powder-coaters on Monday. We are using a modified Fiero front trans bracket, that uses a Dodge P/U engine mount. The stock N* front engine mount is being used. The stock rear Fiero trans mount is being used (Except with a RD poly unit). And the back engine mount is custom, again using a Dodge P/U mount (Can't beat them for $5!). I'll be adding a dogbone up top eventually. We got an aluminum flywheel ordered, I'm not sure how or where, but my friend found it for $400!!! That's the price of a stock Fiero aluminum flywheel! It's in, although I haven't seen it yet. We still need a clutch, going to Clutchnet for that (I've heard enough Spec horror stories that I won't ever go back).

The real pride and joy, the headers. My friend gassed up the welder, and said he'd buy all of the materials if I would build him headers. I started my new job, and am aching to get back into working on projects like this, but am saving my own money for a Jeep SRT8, so I jumped at the opportunity. The headers will be long tube, equal length, 180*. I just can't get over the sound they give, it's biblical. However as we all know, that's not going to be easy. So I'm going to order the piping, and see what I can come up with. Fortunately, with the 6500rpm redline and tame 275 cams, the primary lengths will be long (I'm guessing 36" at least), so I've got plenty of distance to get the collectors placed right to feed from both banks. I actually think I'll have plenty of room for the headers themselves, from the looks of it so far, my 3.4 was far tighter on space constraints. My problem with this is going to be the exhaust. I really want to run dual mufflers and a true dual exhaust, as a single muffler is too loud. However, we also want to keep the trunk, which severely limits exhaust options. Since the swap is still in its initial stages, I've got time to plan. I'm open to ideas.

No pictures yet, I'll take some of the cradle and mounts tomorrow. Here's the car:

https://img.photobucket.com/albums/v...ero/Fiero4.jpg
https://img.photobucket.com/albums/v...ero/Fiero2.jpg

The old engine, roughly 220hp:

http://img.photobucket.com/albums/v3...ro/Engine1.jpg
http://img.photobucket.com/albums/v3...ro/Engine5.jpg
http://img.photobucket.com/albums/v3...ro/Engine6.jpg

Pics of the new motor and the cradle/mounts. The motor is dirty and needs painted, but it is fresh on the inside.

https://img.photobucket.com/albums/v...p/P7250001.jpg
https://img.photobucket.com/albums/v...p/P7250002.jpg
https://img.photobucket.com/albums/v...p/P7250003.jpg
https://img.photobucket.com/albums/v...p/P7250004.jpg
https://img.photobucket.com/albums/v...p/P7250005.jpg

Got the cradle back, looks spectacular. Full sandblast and gloss black powdercoat. The prices went up, but with the economy I'm not surprised. Worth it to have it done right. Next step is wiring, and collection of parts/design for the 180* headers.

https://img.photobucket.com/albums/v...p/P7310001.jpg
https://img.photobucket.com/albums/v...p/P7310002.jpg
https://img.photobucket.com/albums/v...p/P7310003.jpg

I also ordered the header piping. 24 1.625" U-bends, 3" radius, 8" legs. 2 N* head flanges, 2 4-1 formed weld-on collectors, and 3 2.5" U-bends, 3" radius, 10" legs. All mandrel bent, 18 gauge mild steel. Should make for a good start. They should be here this Friday 4-17.

Looks like a pretty nasty project

Kick ass project. But am I the only one who thinks fieros look like min 300zx's?

Thanks guys! It should make for a great driving Fiero. Smooth, torquey, and power to go with it. I think it will leave a bit to be desired power-wise, but we'll see. I'm hoping for around 275whp on the dyno, so it should be good for mid 12s pretty easily. I guess that's not bad, but I've never been overly impressed with the N* overall. I hope I am by this one though.

I see the similarities, but I definitely would go for the Fiero personally.

son of a bitch...---- the old motor is nice i remember when i had my lumina z34 fucker would burn 1,2,and 3 lol...and you got a even bigger and better block...some of a bitch dude..nice man

The n* swaps kick ass.

If you need parts, these guys only deal with N* highperformance parts.

chrfab

That's where I got the idea from, I had a Z34 with a 5-speed that had 40whp over stock, fun car, but it was very poorly designed (The interior especially!). So I started putting the motors into Fieros. Save 600lbs, and gain a bit of power. Much more fun! Here's the build thread of the black car in my signature. It's got a highly modified 3.4 DOHC, and it ------- screams.

https://www.homemadeturbo.com/forum/...ap-custom.html

I've checked their site out, and I'm not really interested. Most of their stuff is really overpriced, and the stuff that isn't, is stuff that I don't really want. The head/cams package has some really impressive figures, too impressive. I'm not sure if I believe the power gains they advertise. Not just that, but the CHR cams take away from everything the N* is all about: Smooth, civil, linear power. I'm afraid with the CHR stuff it'll lose a lot of its civility, and become much more of a Vtec like motor that needs to rev. And while I don't mind revving, I want the smooth midrange from this motor.

Now, if I decide the 275whp isn't enough, I do have some ideas. Well, an idea. I've been tossing around the idea of a custom intake manifold, with a Whipple twin screw blower on top. Really expensive, but I'll just be doing the work, not paying for it!

Go big, or don't go at all!! :) Don't stop at 275!!

Looking great so far. I can't wait to see how this turns out.

Added an aluminum flywheel to the mod list. I think it's about 9lbs, but I'll weigh it this weekend. I think with the CAI, aluminum flywheel, A/C and PS delete, 180* headers, good exhaust, we can hit 275whp. Time will tell, it's going to be a while before dyno time. I'm really not happy with my friend deciding to use the 7730 OBDI ECU, I'd really like to see it use OBDII, but oh well, maybe he's better at tuning than I think.

More power would be great, but this does have a budget. Unfortunately, I messed up giving the credit card number to the guys at Stahl Headers, so I may not have the materials this weekend. That would really ------- suck.

awesome car man

def going to be following this one

nice :)

N* are nice...for about 1/2 of year a few years ago i got to borrow my dead grandfathers '98 Deville with the 300horse N*...fucker hauled the mail. i took it street racing many times, beat alot of cars...plus the e-brake was on the floor, but won't lock if the car is out of park...so drifting was very easy...ever seen a '98 deville do a scandivnavianan flick with a light jab of the e-brake to initiate a drift at 70 mph on an offramp...tis awesome

the most fun couch i've ever driven...plus if you leave the shifter down in 1st...& go WOT it will chirp 2nd gear...but of course, your running a manual...bastard, lol, damn i wish i was allowed to keep it, but my rich uncle sold it...so he can more money instead of letting me keep it...grr

sOUNDS LIKE A COMBO FOR FUN

Still no header pipe. Next weekend I guess.

Maybe my friend will stop being lazy, get the engine on the cradle, and get the coolant crossover/water pump on next week too, that'll help with the header design.

looks good

It sure is nice to look through a thread and not see any ------- hondas

I know it's uncommon around here, but like some others, I too want to see more "different" builds. There are too many of the same thing over and over again. So hopefully you guys enjoy seeing some red white and blue in this sea of red and white :)

Update. Got the motor on the cradle, looks fantastic and sits straight and level. The aluminum flywheel came in, and I started working on the headers.

http://img.photobucket.com/albums/v3...p/P1010007.jpg
http://img.photobucket.com/albums/v3...p/P1010010.jpg
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Primary dimensions are 1 5/8" by 41" long, tuned for a 4500rpm torque peak. The header you see will be my lower one, collecting cylinders 2, 3, 5, and 8. The primary for cylinder 2 is mostly complete, other than that, it's slow going, and a royal ------- pain in the ass. Hardest set of headers I've built, by ------- far.

lovin the project!

That fiero looks clean as hell, can't wait to see some vids of this thing tearing ---- up!
Good luck!

Isn't 38mm wastegate too small for that kind of setup, any boost creep..?

For the car in my sig? No boost creep at all, up to about 7400rpm. 38mm seems small, especially with really low boost, but it's working great. I think that's mostly do to how well designed the exhaust system is, the wastegate is all of 2" away from the turbo, the feed back to the exhaust is smooth and mandrel bent, and it feeds from right at the Y. I can't really explain it, as looking back it does seem small, but it works!

I see, just wondering because I had boost creep at 17lbs, now I upgraded to 44mm will see haw its gonna work.

With how much power? The amount of power is much more so an accurate representation than boost pressure, unless the motors are the same. It's going to take more exhaust to make more power. So while your 17lbs is greater than my 9, if I'm making a lot more power still, I'll use more exhaust volume, thus less is going to the wastegate.

I hope the 44 works out for you, sucks how much more they cost! Also, you running a name brand? I've seen some tests showing that the name brand, top shelf pieces flow a lot more volume per mm valve than a lot of the imitation pieces.

Your wright I had 390whp, I had to pay $345 for that Tial... lol
Dont ask me haw much I paid for that brand new GT37r, I hope everything is gonna work just fine.

Huh, I wouldn't think 30whp would make that much of a difference though. Probably has a lot to do with how the exhaust system is setup. Headers or manifolds, how the wastegate is positioned, T3 vs T4 housing, different wheels, etc.

Sounds like you have some pretty nice components, link to a build thread?

Yah I had no room for that wg dump pipe, so I had it like this.

Attachment 8377

Attachment 8378

I finally got an update. I had a free weekend to work on the headers some more. We also picked up a set of the higher output cams, so that'll make this a 300hp variant, not 275 like we had originally. Plus, the header lengths are tuned for a 300hp N*. So far I've got the tubes for cylinders 2 and 8 done, I'm hoping to get tubes 3 and 5 finished tonight and tomorrow. This set hangs about 1/2" below the oil pan, and sits even with the bottom of the cradle, so there won't be any ground clearance issues. In the second to last pic, you see some weird looking pieces of metal shoved in between the flanges, that's to simulate gasket thickness, so they won't stay there hehe.

http://img.photobucket.com/albums/v3...p/DSCF0037.jpg
http://img.photobucket.com/albums/v3...p/DSCF0032.jpg
http://img.photobucket.com/albums/v3...p/DSCF0033.jpg
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http://img.photobucket.com/albums/v3...p/DSCF0035.jpg
http://img.photobucket.com/albums/v3...p/DSCF0034.jpg

Nice build. I was wondering if you thought about going with a supercharged 3800 motor instead of the north star? If so, why did you choose the n* (not knocking you just wondering what are the benifits )

NICE.

I hate the 3800. They're a dime a dozen, are not fun or exciting to drive, and sound terrible.

Looking at the facts, the N* really doesn't have a benefit, except it'll give mid 12 second quarter miles right out of the box, and drive like a Cadillac. But the 3800 is just like a small block with a carb. It's unrefined, and everybody has one.

1. not all 3800's have a carb. i have an efi 3800 in my buick.

2. How the hell are you fitting a v8 into a fiero anyway??!?!?!?! i didn't think that was possible! those things had no room in them when it was just the crappy little i4. anyway, good job. i can't wait to see it finished.