Hey guys, ever since I've been on this board I've been keeping track of the different engine swaps and deciding what would be best for my "needs". I think out of all the engines that can be stuck into a Fiero, I've come down to 2 swaps that I can't really decide on. I originally wanted a V8 Fiero, but to be worthwhile it'd have to be a N*, LT1, or LS1 (I want more advanced technology so I don't want an ancient 350), but the prices are too high and gas economy isn't all that great. I decided on the 3800SC several months ago but then I saw several threads with the 3.4 DOHC and it seems like it might be the better choice. So, I have a few questions because I'm not sure of what I want, and I just got my Fiero that will get the engine and I'll probably get it put in this summer.

1. This is the most important, who does the 3.4 DOHC swap? I know that Loyde out in Dallas will do the 3.8SC and he is an absolute MASTER of that swap, but I don't know anyone off hand who does the DOHC? I am a novice mechanic and I don't have a very large working area, I am pretty sure I couldn't do this swap on my own. I can only use my garage here for 2-3 days at a time then I have to be able to leave the car outside.

2. How much would it cost to get a DOHC Turbo put into a Fiero? Loyde, on his website, quotes $8800 to put a 3800SC into a Fiero. And I want the 3.4 to either be Turbo or S/C, not N/A.

3. How reliable and easy to work on is the 3.4 DOHC with a Turbo on it? The 3800SC seems like it would be more reliable since GM gives GTP's warranties with that engine in it, and Loyde backs up his work.

4. What kind of gas mileage does a 3.4 DOHC Turbo get, when compared to a 3800SC?

5. Which engine is lighter weight?

6. Which do you think I should put into my car?

7. What does the 3.4 DOHC redline at? 7000?

Please, keep this thread civil. That means AaronZ34, behave yourself.

Oh, btw, the car that this is going in is a '86 SE 4-speed with 133,000 miles on it.

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I am the signature virus, please put me in your signature so I can spread

quote Originally posted by Formula88: Might as well cut the crack pipe out and put the joint in there.

My vote is for the Turbo DOHC. Not many people chose that route That's what I want to do eventually

[This message has been edited by fiero_silva (edited 12-22-2005).]

*Civilness level 9 enacted*

1.) No one "does" a 3.4l DOHC swap. But PFF member Erik can make you a plug and play wiring harness, and from there it is basically a 2.8l replacement with 88 mounts. You would need to route the coolant and fuel lines, and cut the decklid hinge. I would do the 3.4l swap for you, but I want to have mine done before I do it for anyone else.

2.) Rough guess...Figure about $1000 for a motor that can handle a turbo, $3000 for the turbo kit, $1000 for the swap, and that should be about it. So roughly $5000, add $1000 for misc.

3.) The 3.4l DOHC is just as reliable as a L67 if you get a motor that has been well taken care of, and you take care of it. Synthetic oil is a must, timing belt changes every 60k, etc. So long as you keep on top of it, it is a good motor. But if you are buying used motors, I'd say go for the 3800. The 3.4 is just as easy to work on once you know how to work on it.

4.) A 3.4 DOHC should get the same, if not better mileage than a 3800, even with a turbo on board.

5.) They are about the same IIRC.

6.) 3800, because I honestly don't think you have the mechanical inclination and resources available to build, tune, and maintain a turbo 3.4 DOHC.

7.) Factory redline is 7000rpm.

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"all pushrod motor are better than the dohc because it has less rotational mass"
-rick17, MyMonte member, owner of a 3100 Monte Carlo LS

93 - N* Fuel ------- 16 city 25 high way.
93 - 3.4 DOHC Fuel ---- 17 city 26 high way. (N/A STOCK)
97 - 3800 S/C Fuel ---- 17 city 27 high way. (Supercharged)

www.fueleconomy.gov

What I don't understand is your logic behind these gas emissions theories that made you take out the N*.... Because it gets almost the same as your other two options, if not better when you start to factor in your upgrades to the turbo / supercharger. When you start adding more PSI to a smaller engine you are going to naturally lower your fuel economy for more power. The fun thing with the V8 is that you can do a quite a few mods that will increase your horsepower and your fuel economy..... As I am sure you other motors can as well.

I am not "dising" any of your choices, however you shouldn't be so quick to judge.

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Custom Fiero Fiberglass

actually i think maybe two people might do the dohc swap for you, or at least it might be worth asking them about it if you're serious. either darth fiero or pbj.

quote Originally posted by Custom2M4: When you start adding more PSI to a smaller engine you are going to naturally lower your fuel economy for more power.

you are misconstruing the information, especially with turbochargers which only build boost when you want them too.. they do not boost at all just cruising so you are infact getting stock milage if its tuned properly..

as for the argument of how often do you get on it.. at that point the displacement becomes a moot point and only the amount of HP and a/f ratio calculate out to an actual measurable fuel usage..

plus everyone knows the EPA ratings are just general guidlines.. the 3.4's behind 5speeds are getting about 30mpg - the 3800sc even modded are getting 30's with their 4speed auto, not sure about the N* - it would really depend on the tranny used.

Normaly Id say if you wanted something super reliable, go with the 3.8SC its the longest running V6 in history, like over 30 years production, proven strong, proven reliable.

However, it looks like you're willing to throw some serious money at this. The 3.4DOHC is marginal as far as reliablilty goes, but if you're willing to build it right, it could be just as reliable. Wish I had a bigger shop Id be doing swaps.

As far as cost, my swap with turbo, less than $1400, but thats doing EVERYTHING myself.

I think the 3.4DOHC is a breeze to work on.

dunno turbo, but realistic MPG 3.4DOHC is 15-18 city rough driving, 20 if you're nice and lucky, 28 highway babying it.

dunno about weight, my 88 GT full option, 3.4DOHC 5spd w/o turbo setup is like 2800 lbs w/o driver

I LOVE the 3.4DOHC, but kinda thinkin the 3.8 would blow up a touch less... but then again, Im pretty sure its my complete lack of giving a crap so it would be a toss up. Would definitely choose the 3.4DOHC if I knew I would hold up, no question about it, but like I said if you're willing to put in the $$ you shouldnt have a problem with durability.

3.4 redline is like 7150, realistic useable powerband NA is like 6500, though with the getrag 1st gear is useable to redline.

Seein as you have a 4spd you might be a little happier with the 3.8SC's low end torque. The 3.4 gets up and goes great, but having fewer gears, the always there power of the 3.8SC would give you better utilization of the low end.

Well technically they would all depend on the transmissions.. I can see that as well.. Hell getting on it on either of the three you will be using quite a bit more gas, wheither its from larger displacement, or a power adder. I didn't mean to discourage any of them, but perhaps I was trying to get the N* back in the game a little bit there.

It was said that N*'s don't get good milage, and I know of a few people that would argue that all day while driving past the pump. I do like all the above choices, and the choice should be made on personal preference really since they are all fairly different motors...

Do you want a high reving V6 with screaming horsepower until 7200+. Do you want a torque monster V6 with the whistle of a supercharger, or would you want a V8 with decent milage and a really cool look under the decklid! !

Chevy 3.4 liter DOHC V6- 493 lb.

Buick 3800 Series II supercharged- 445 lb.

Just to correct Aaron.

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400HP out of a SBC? Now thats just crazy talk.

The price of the N* is a little bit prohibitive. That is the engine in a dream world ( ) that I would want, or possibly a LT5 or LS1. Plus I don't know anyone who does a N* swap, and from what I've heard its a wiring nightmare and there is no way I could be able to do it myself. Also, can the N* handle a 4-speed or 5-speed manual? I thought all the caddys came with automatics.

Right now I'm trying to sell my Camaro Z28 (LS1, 4-speed automatic), and it looks like I'll probably have around $12,000 to put into this swap. Loyde can do a 3800SC for $8800 so I'd have $3000 left over to put into suspension and brakes. I'm also trying to decide if I should get it changed from a 4-speed muncie to a 5-speed getrag at the same time, from what I understand the master and slave cylinders for the clutch have to be changed along with the shifting linkage?

Custom2M4, ideally I'd want the Northstar, if I can find a way to do it for less than 11gs and with a 5-speed I'll go that route. I see Loyde has the N* listed on his site as a engine he swaps, but he has no info on it. The engine should get decent gas mileage, my LS1 Camaro gets about 18 city and 25 highway and revs at 2000 rpms at 80 mph. 2nd choice, I'd like the 3.4 DOHC because it seems like the proper engine for a sports car because it revs so high and has loads of power. If the Fiero had lived on, I think it probably would of ended up with the 3.4 DOHC in the mid-90's.

86GT3.4DOHC, your engine blows up? Hahahaa I see you're hardcore!

Right now I'm leaning slightly towards the 3.8LSC. No one can do the 3.4DOHC swap for me, Aaron said I can't tune and maintain it, and the 3.8 might be more reliable since its been around longer. It also came from GM in the Grand Prix GTP supercharged and all with a warranty. The warranty shows that GM engineered this engine well with forced induction in mind and they trust it enough to warranty it. I know it won't have the warranty when its in my Fiero .

Although I like the idea of DOHC.... any info on the N*?

Edit: BTW my goal is to have about 300 RWHP in this car, or at least 270. My Camaro put done 285 at the wheels bone stock and I'd like a car that would smoke Camaros, Trans Ams, and Mustangs, and yet still be able to get me back and forth to college with decent mileage and reliability. So a Turbo 2.8 with a 100 shot isn't an option . I know a stock 300-hp N* (came with 300 and 275 hp in different cars?) gets about 240 hp @ the wheels, and a 3800SC gets about 200 RWHP. I don't know what a turbo DOHC gets.... that's the only thing that is keeping me from getting the 3.8, its HP rating.

[This message has been edited by Tinton (edited 12-22-2005).]

umm if not already mentioned but i'm pretty sure darth has done a few 3.4dohc swaps for people ..but of course comes with a price ..i've seen his threads and he knows what he is doing ..i would recommend him for it ...and would make it easy for him to do mine but i want to learn myself ..and he is sorta far away and too much money lol ..i'll save alot more doing it myself and will be alot more fun doing it myself too..but then again will be some headaches...anyways good luck and why did i choose the 3.4dohc myself ..i could get one for cheap

matt

quote Originally posted by Carswell...Wellscar: umm if not already mentioned but i'm pretty sure darth has done a few 3.4dohc swaps for people ..but of course comes with a price ..i've seen his threads and he knows what he is doing ..i would recommend him for it ...and would make it easy for him to do mine but i want to learn myself ..and he is sorta far away and too much money lol ..i'll save alot more doing it myself and will be alot more fun doing it myself too..but then again will be some headaches...anyways good luck and why did i choose the 3.4dohc myself ..i could get one for cheap matt

K, PM sent to Darth Fiero.

quote Originally posted by Tinton: a 3800SC gets about 200 RWHP. I don't know what a turbo DOHC gets.... that's the only thing that is keeping me from getting the 3.8, its HP rating.

please elaborate.

quote Originally posted by Tinton: Edit: BTW my goal is to have about 300 RWHP in this car, or at least 270.

Tinton, if you want 300RWHP I recommend you get an engine that can develop that in stock form. With the DOHC or SC you are going to have to do some work and then maintain them. Both have to be pushed with $$$$ to get to those levels and unless the efforts and cost are intuitive to you I think you would be better off maintaining an engine that has the power you want without pushing them. I know that doesn't leave too many options.

IMO.

[This message has been edited by TK (edited 12-22-2005).]

quote Originally posted by 86GT3.4DOHC:As far as cost, my swap with turbo, less than $1400, but thats doing EVERYTHING myself.

You should include that spending $1400 on a turbo setup has caused you a blown motor, which certainly won't be cheap.

Sorry UDLOSE, I was off by 48lbs...Big deal. And I didn't say they were identical, I said they are about the same. And within 50lbs is "about the same" in my book.

50lbs is .05 seconds on the drag strip....

quote Originally posted by UDLOSE: please elaborate.

I got both my cars dynoed last year at Ed Parks swap meet. My Z28 put down 285 hp, my '88 GT put down 107 hp. There was a Fiero there with a Northstar, I forget his name on the forum but it was a purple convertible N* and it got like 240 hp at the wheels if I remember correctly. There was a car that had a 3800SC, it got like 200 hp.

Ok, since 300 rwhp is a little much and the only way to get that in a stock engine is a LS2, LS6, LS7, LT5, etc, I guess that goal is a little too much for the amount of money I'm talking about? How much money does a Northstar cost to install, does anyone know? Its probably going to get the closest to the kind of power I'm talking, at least in stock form. And a 3.4DOHC turbo puts down 200+ rwhp?

quote Originally posted by AaronZ34: You should include that spending $1400 on a turbo setup has caused you a blown motor, which certainly won't be cheap. Sorry UDLOSE, I was off by 48lbs...Big deal. And I didn't say they were identical, I said they are about the same. And within 50lbs is "about the same" in my book.

Blown motor:

New piston $40 shipped
Head set- conversion set - rings $111 shipped

Boost - Priceless

Ignoring the fact that the only reason it blew up was because I was racing a completely untuned engine on 89 octane. Course I was thinking in the back of my mind, that if it broke, I could have a reason to put in new rings and find my low oil pressure problem, and I had to park it for the winter. Definitely worth it

Now technicaly I replaced 3 pistons, but the other 2 that were cracked were unrelated to my detonation problem, plus I got new rings out of the deal. Had it not "blown up" The other 2 cracked pistons would more than likely have gone the same route as the last engine that literaly blew up, I couldnt find anything from piston #4 bigger than a quarter, and the rod bent, warped and twisted. Im almost positive a chunk of the ring land broke off. I pulled off the intake to find a piece of piston ring literaly hanging out of the throttle body, found piston in the intake, and jammed in the #1 intake valves

As far as the wieght, Ive seen so many diffrent numbers Its hard to know whats right, but im sure its all in the ballpark. I would like to come up with some way of weighing my engine before I put it back on the tranny, get a complete every nut bolt and accy weight with wiring. Would leave the flywheel off so that it wouldnt factor in to an auto-stick confusion. Im trying to figure out how. I can think of a couple of ways, 3 bathroom scales, each could handle 200+lbs, one under each wheel of the engine stand, then subtract its wieght. But I dont really have money to just blow on scales Id never use again. Other option would be a hanging balance, I could use an unequal length shaft, engine on one end, then 12" then hook, then "36 then weight, Would only need about 125 lbs on the other end, but I cant think of anything strong enough not to bend that I could get for cheap. Maybe some 1" box steel?

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Boost is like Venerial Disease, one night of passion can result in weeks of pain (and work.)
http:\\www.myspace.com\keeptherubbersidedown

1. Didn't Darth do one for someone else in his build thread a while ago. West coast fiero might do one. Gonna cost you though.

2. Dunno.

3. I think the 3.4 is not too bad to work on, pig having to pull the plennnum to pul the rear cam cover though since you gotto replace gaskets you would not touch otherwise (ka-ching...), and earlier engines have a lock ring for the cams that's a pain to work with I think. Otherwise from my limited work on it (only done cam timing, 95 engine) it seems pretty easy. A turbo is just another component to work with and other than the oil feeds is largly external to the engine itself.

4. I get 20 mpg, 60% surface, 40% freeway and a heavy foot when the ligh goes green (just too much fun not too LOL).

5. Dunno but I do know the the DOHC is dang heavy. Those heads and cams add a LOT of weight.

6. Having done the 3.4 I'd say the 3800 SC. It's already supercharged, especially with an automatic tranny, the 3.4 goes well with a manual but most cars are autos. Seems to fit better in the engine bay from pics I've seen. Probably more tuning options for a 3800 as well than the 3.4. With the 3.4, especially if you add a turbo you are in uncharted territory. I know some have done it (Christ West of WCF at least) and some are working on it but do you really need to lead the pack. Remember if you pay $8k plus for a swap it had better be reliable and beleeding edge anything rarely is.

7. 7k I believe but my tach needle hits the oil pump needle (old 4 cyl setup still and not recallibrated yet). Loves to rev though and yet slugs along quite happily at 2400 rpm in 5th (issuzu box) doing 70mph.

Final piece of advice. Decide what you really want from the swap, raw power, reliability (hard and expensive to have both), something differenet (expensive and probably unreliable) and budget and build that. At the end of the day you probably want to spend more time driving the car than working on it (well I do anyway), works out cheaper that way so simple, affordable, reliable is the way to go. If you have the time, money, resources (garage space, tools) and another car to be a daily driver then go bleeding edge. Otherwise you'd better have good bus service where you live LOL.

Just $0.02 from an older guy whose been there, done that (but hey, who listens to us old guys anyway LOL). Y'all have a merry Christmas (or holiday of your choice).

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Dave E

www.ltlfrari.com

[This message has been edited by ltlfrari (edited 12-22-2005).]

The N* swaps I have seen were of quite a few standards. One locally with an 87 GT and a 5 speed. So that won't be a huge problem. That purple N* convertable was for sale for 15,000 I do believe :P !

quote Originally posted by Custom2M4: 93 - N* Fuel ------- 16 city 25 high way. 93 - 3.4 DOHC Fuel ---- 17 city 26 high way. (N/A STOCK) 97 - 3800 S/C Fuel ---- 17 city 27 high way. (Supercharged)

Those numbers are meaningless. The N* wont be in a 4000 lb Caddy. The 3.4 DOHC wont be in a 3400 lb Lumina. The 3800 S/C won't be in a 3400 lb Grand Prix GTP. Thes donor cars also all have different transmissions with different gearing.

i know this wasnt on the debate, But if you want 300HP reliably, why not get a 5.3L from one of the new chevy trucks (they even offered an all aluminum one) be the first person on the forum to put a 5.3L motor in their fiero also. lots of aftermarket arising for those motors as well, and if you want to go all out, you can get the 6.0L from a 3/4 ton or larger chevy truck, but i dont know if its bigger (outside size) than the 5.3L or not, the 4.8L and 5.3L are the same casting and block, so id just recommend the 5.3L if you have those options.

If your car's an automatic now, get a 3800 series II supercharged, you just cant beat its reliability, and power

i say that to you, and i own a 3.4L DOHC motor bolted to a fiero 4 speed trans, just waiting to install it. and look ^ what i recommended.

matthew

I say do the N* or 3800sc - because for a while I was going to be the 3rd or 4th person to have a 3.4dohc turbo and now everyone is doing them

well, got no real info on either motor - so this is just a general statement - if you do more dragracing - do the 3800sc, if you do more road racing - go with the 3.4DOHC. either one makes the Fiero an outragous vehicle. in the 1/4 mile list - the 3800SC is pretty much it. and the reason I think the 3.4 for road racing is higher revs. since you dont want to shift in a curve - the longer rev range gives you slightly more options on what gear to be in.

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1985 Fiero SE - Plain Red V6 Coupe
3.1 Crane272 MSD 4.10-4spd DarthChip Borla
D.A.M.M. - Drunks Against Mad Mothers

quote Originally posted by Scurvy: 50lbs is .05 seconds on the drag strip....

Exactly my point.

Yeah, Id listen to Aaron if I were you.

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400HP out of a SBC? Now thats just crazy talk.

quote Originally posted by Scurvy: 50lbs is .05 seconds on the drag strip....

if someone is a good enough driver that .05 seconds makes a difference then more power too em for losing 50pounds

quote Originally posted by Kohburn: if someone is a good enough driver that .05 seconds makes a difference then more power too em for losing 50pounds

Shaving 6 pounds off your car is equvielent to gaining one horsepower... So shaving 50 pounds is like porting your exhaust manifolds.

I just know that as a rule of thumb every hundred pounds you shave off you car is good for a tenth of a second. I know weight reduction in the fiero is hard to do where it'd make a big difference but if you are in a 3500lb boat and can easily shave 500lbs then that's some serious gains

Tinton: There's a good article in High Performance Pontiac, March 06, about swapping in a turbo on a 3.8sc, 400hp at the wheels. This would have you in the low 12's or high 11's. And should still get 30 mpg on the highway.

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85 GT 3.4
Auto 3.08
14.9 @ 90 1.9 60"

quote Originally posted by Lilchief: Tinton: There's a good article in High Performance Pontiac, March 06, about swapping in a turbo on a 3.8sc, 400hp at the wheels. This would have you in the low 12's or high 11's. And should still get 30 mpg on the highway.

300whp is low 12's - 400whp is low 11's high 10 territory

Either way it would be d*mn fast, and very very few would beat it , at least street legal.

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85 GT 3.4
Auto 3.08
14.9 @ 90 1.9 60"

Exactly, sorry we aernt really being too helpful in the decision process. I HATE to dis my favorite motor, but I really think for realiability the 3.8SC would be superior. I have a friend with a 99Regal 100k+ modified, putting down 9psi boost daily, and he beats the living hell out of it. On his 2nd or 3rd tranny, but the engine is doing fine. Then again I beat the living hell out of my car 7k daily, and once I got my hands on a good engine, it held fine until I pushed it stuipid far.

quote Originally posted by Kohburn: spitting out numbers like that can be misleading - the acceleration change from weight loss is relative to the starting weight - its a percentage, not linear. and my point was that most people will gain or lose 2-3 tenths just depending on their launch

exactly. its just changing the hp/weight ratio. a 4000# car with 100 hp will not gain much from losing 50#, while a 2000# car with 700 hp will gain ALOT.
like little Danika Patrick in the indy cars. her 90# gives her a nice advantage over other 150# drivers
and of course, the midgets riding real horses. 1hp lol
but, as a generality, it is a good "rule of thumb" - 1 tenth for every 100#
and yes, for newbs - launch & shift points are much more important than trying to drop 100#

m0sh_man, that's an interesting engine. I was thinking about the 5.3L engine from the new Grand Prix GXP's, it is the LS4 and has 303 hp and 323 lb ft. That's probably around 250 rwhp and 270 rwtq. A northstar gets that much power and it has been swapped into Fieros before, and it has that cool-factor of a 32-valve V8. No one has put the LS4 into a Fiero yet? I'd say it'd be a great swap since its being used transversely in the Grand Prix, but I doubt there'll be many in junkyards for a few years.

I really want the Northstar because it looks like it gets about the same mileage in a 4000 lb car as the 3.8 and 3.4 get in 3400 lb cars. And it can be used with a getrag 5-speed as some people have said. Only a couple of questions on it, how much does it weigh? My other question, about price, will be sent to Loyde @ FastFieros because it looks like he can do the swaps. If its too expensive I'll probably go with a 3800SC. Darth Fiero replied to me and said that the 3400DOHC is actually a pretty weak motor stock and to handle anything over about 4-5 psi boost it needs some modifications, which of course cost money. With mods it would probably cost the same as a 3800SC swap? He quoted $2700 for labor for the DOHC, but then I'd have to pay for the motor and other things.

BBL Fiero dudes and dudettes .

A pushrod iron head engine that GM had to slap a SC on to make power
OR
A dohc that with a turbo pushing the same boost as a stock 3800sc makes 325 wheel hp.

55hp more in a engine that revs 2000 rpm higher... what else would you need to know?

quote Originally posted by DOHC_SWAPPER: A pushrod iron head engine that GM had to slap a SC on to make power OR A dohc that with a turbo pushing the same boost as a stock 3800sc makes 325 wheel hp. 55hp more in a engine that revs 2000 rpm higher... what else would you need to know?

Lets not go this route.

Stock 3800SC is the key word. There is no stock 3400DOHC Turbo.

N* weighs aound 470lbs IIRC, not including the tranny. (4T80E)

[This message has been edited by UDLOSE (edited 12-23-2005).]