hey guys, i am wondering if any of you guys can give me the pros and cons of the 3.4DOHC and Pushrod swaps? I would like to know the gains of them, the difficulty of install and which is a more street racing and or strip swap? thanks-Frankie
The pushrod 3.4 is somthing that can be done in a weekend and does not require rewiring of the whole car. I think the only thing that is needed is either a starter relocation or alternator relocation. It bolts up to the stock fiero motor mounts and used the stock fiero heads and plenum. Basicley a very very easy swap compared to others. This engine block is commenley pulled out of the 93-95 or 96 camaros or firebirds
DOHC will take you some time. You have to do some rewiring and I beleave motor mount work.. Not as hard as other motor swaps but not as easy as a 3.4 pushrod. This engine i think is found in newer style luminas and 90's motie carlos.
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04:34 AM
BL3200 Member
Posts: 131 From: Harze, Liege, Belgium Registered: Oct 2009
On a pure technical point of view, DOHC is better than pushrod because in DOHC you don't have rocker arms nor pushrods and this means less friction and less power required for valves opening.
------------------ Bernard Fiero V6 GT 1987 (Manual)
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07:11 AM
TopNotch Member
Posts: 3537 From: Lawrenceville, GA USA Registered: Feb 2009
I'm not familiar with the 3.4 DOHC, but I do know that many overhead cam engines do have rocker arms. That is, the cam does not push the valve directly, but pushes a rocker arm which in turn pushes the valve. It does this to get more valve lift than the cam alone would give.
PR = drill block for starter, swap over all Fiero 2.8 top end stuff to the 3.4, install and go. DOHC = a lot of fabirication and wiring + new ecm.
I'd never done an engine swap before and the DOHC was pretty easy overall. That said, there's no such thing as a 'kit' for it, you are pretty much on your own for everything and you'll need to fab your own exhaust system as well as several other parts. It's not hard if you are good mechanically and have the tools (or have access to them or can buy them)l You'll also need to either mat the DOHC engine harness to the Fiero's harness or make a custom harness (which is what I did) as well as use the DOHC ECM (couple of people on here will burn you the necessary chip). You'll probably also need to upgrade the car's rear suspension, the DOHC is heavy.
On the down side there's pretty much NO off the shelf performance stuff for the DOHC so for anything above the stock motor, you are on your own.
I havent done a swap but just looking at others threads 3.4 looks like it is a drop in and go. the DOHC looks to be a bit harder but not to bad . As far as preformance the 3.4 DOHC has so good of heads that they flow enough air to make 350 HP + N/A but that would come at real high rpm like 9000 + so the bottom end would need beefing up.
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10:30 AM
faalvino Member
Posts: 294 From: Ellenville, New York Registered: Oct 2009
The 3.4 DOHC motor will make more HP due to better heads and intake. What is more important to you: hp, cost, ease of swap????
I am looking more towards hp but cost needs to be under 2500$ if possible. Does the weight difference between the DOHC and pushrod mean alot? i heard the DOHC significantly weighs more
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10:55 AM
FierOmar Member
Posts: 1646 From: Glendale, California, USA Registered: Dec 2001
Do you need to buy major tools, cherry picker, welder etc and if so will the cost come out of your budget?
I spend 18 grand on mine in total!. OK, I did a lot of stuff the hard way in that I would make something myself that I might have done cheaper, particularly in the a/c area. I also spent a lot on tools and possible 'solutions' diagnosing what turned out to be a wiring issue.
Can you do it cheaper? Sure but be realistic about the costs as well. If you need to buy major tools or farm work out (like the exhaust system), factor that cost in.
I had mine mated to a 5 speed issuzu and it was great, loped along at 2500 rpm at 70 mph. Only down side was that the spread between 1st and 2nd gear was a little wide and my box was real slow to shift between those gears so it's scream in 1st but buy the time I got it into 2nd the revs had dropped off and it was out of the power band. It'd pick up no problem though and it was great to just be able to push the throttle and 'go', pretty much in any gear at any speed.
Can you get more power out of the motor? yes. Cheaply? no!
There is the so called 13 degree cam timing change you can do that moves the power band around a little but I never did it, I preferred reliability over unusable performance and in that respect the motor was great. Once I had it running it never missed a beat and I always had a grin on my face driving it.
I'd do another except I have too many things to do to both my cars right now just to keep them running and I'd like to stay married as well!
If you want cheap and maybe future tuning options I think you might be better off doing the PR engine now and maybe turboing it later.
The pushrod 3.4 is somthing that can be done in a weekend and does not require rewiring of the whole car. I think the only thing that is needed is either a starter relocation or alternator relocation. It bolts up to the stock fiero motor mounts and used the stock fiero heads and plenum. Basicley a very very easy swap compared to others. This engine block is commenley pulled out of the 93-95 or 96 camaros or firebirds.
The engine is only pulled from 93-95 Camarobirds, no '96s nor any other vehicles. I made that "weekender" statement, but it needs some clarification here because this makes it sound far too much simpler than it actually is. It is the easiest swap, but it's still a major project. A 3.4 pushrod swap can only be done in a 3-day weekend by at least two people who have done it before and have all the swap parts and tools they need on hand; a clean, rust-free chassis with no frozen or damaged chassis bolts; and an engine with no electronic, electrical or vacuum-related problems. Mechanical problems are OK but everything else has to be in good shape.
- The alternator is not relocated. Only the starter. - If you have A/C there are some additional adaptation parts you'll need. - On an '87 5-speed you will need a different flywheel or need to modify the one you have for neutral balance. - Unless they're brand new, you will need to replace all engine and transmission mounts (this thing has enough torque to shred anything that's got miles on it) - You'll need a complete replacement gasket set. - You will likely find items in need of repair or replacement, either from the fragility of aged parts or your own mistakes, so be prepared for additional costs. Connectors break, vacuum lines crack, hoses split, etc. - The 3.4 balancer needs to be modified with a new timing mark. - This is at least a 30-beer job, so stock that fridge and keep it stocked. S.O. participation: "Sure honey, you wanna help?"
I second that, it's a 3 day job. I have a lot of experience with Fiero's and it was 2 days of hard work, and just button up and drive on the third. Sure it could be done quicker in a shop setting, but for the normal knowledgeable Fiero person, its really a 3 day job. But it is only the slightest bit more work then just replacing the motor.
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02:29 PM
faalvino Member
Posts: 294 From: Ellenville, New York Registered: Oct 2009
Thanks a lot guys this all sounds great but im not the most fiero savvy person...i have done alot of work with camaros and mustangs but i have never really worked on a mid engine car. I am definitely not the type to do this but would it be better for me to have a mechanic do it? if so what kinda cost will that run me? or would it be something i could pull off with a good amount of time?
If you can remove and reinstall an engine in any car, you can do a 3.4 pushrod swap in a Fiero. It isn't that much different from any other car, in fact in many ways it is easier (like not having to mess around with a steering rack). But if you pay a mechanic to do it for you, you will also be paying for that mechanic's time to learn how to do it, and there is a multitude of opportunities for one to fudge numbers and inflate costs. Fiero engine swaps are best done by yourself, or failing that, by the handful of vendors that specialize in a particular range of swaps. It's also a crash course in the car that will be invaluable to you when problems arise.
1 person with a reasonable amount of tools and armed with the knowledge of this forum can do it. It will take more than a 3 day weekend though simply because you will break rusted bolts and have to go to the hardware store or split a rubber hose and have to go to the auto parts store. It can get time consuming. As stated above, it's a great learning experience. I replaced every bolt and nut that was rusted with stainless steel if possible (10.9 hardness SS bolts are not that common, 8.8 SS a little easier) It's the little details that get you. Rusted cradle bolts, broken exhaust bolts, and on and on.
The two are totally differant. One is a high reving motor that makes its power in the upper RPM band, the other is a used in MiniVans.
The 3.4DOHC block is the same as the stock 2.8L, so it uses the same motor and trans mounts. the motor fits with a small amount of fab, to the dogbone mount location and the pass side trunk lid mount (firewall location). Easy, breazy. Exaust will require some fab depending on how you want to run it. Some remove the lower portion of the trunk, or you can have a "Y" pipe fab'd up and run it the stock way. I used a set of headers. WIre harness is the long pole in the tent, but can be done. Hell, I did it. Cost - I would say the 3.4 PR is prob cheaper, and you may find a few with low miles. No aftermarket support for the DOHC. If these are your only options then again its what you want.
I'd suggest the 3800SC or if mony is no option go with an LS3.
Rob
------------------ 88 TTop coupe (96 3.4DOHC/5 speed) 03 Vibe GT. 6spd (stock) 05 GTO, LS2, 6spd (not stock) 84 SE "Vert" (oh boy, what did I do now)
Originally posted by qwikgta: The 3.4DOHC block is the same as the stock 2.8L, so it uses the same motor and trans mounts.
You mean the 3.4 PR engine is the same block in comparison correct? The 3.4 actually has a lot more beef built into it compared to the 3.1 or 2.8, even though keeping the same aspect and style of the former two. I believed GM redid the mold for this block to have thicker webbing around the pistons.
I second the motion of the 3800 SC. I have toyed with what to do with mine, and it would be simple to swap in a 3.4, but for what gain, little... may as well save and plan for something noticeable, like the 3800SC.
------------------ Brent 1988 Formula - Fastback Coversion **CJB T-Tops**
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10:45 PM
Nov 2nd, 2009
Mickey_Moose Member
Posts: 7568 From: Edmonton, AB, Canada Registered: May 2001
Nope, one can also find the 3400 in a 96 Pontiac Transport - not sure about any other years/models.
You mean the 3.4,not the 3400 right? There is also an HT3.4 available as a crate engine from GM dealers. It is a high torque upgrade engine for S10 trucks/SUV's originally equipped with the 2.8l.
Originally posted by crazyd: The engine is only pulled from 93-95 Camarobirds, no '96s nor any other vehicles.
quote
Originally posted by Mickey_Moose: Nope, one can also find the 3400 in a 96 Pontiac Transport - not sure about any other years/models.
I'm sure you mean well, but let's not confuse people, Mickey_Moose.
The pushrod 3.4L engine that crazyd references is different in design and simpler to swap than the "3400" engine you'd referenced. Accordingly, in addition to any pushrod 3.4L crate engines, the statement made by PFF member, crazyd, is quite correct:
quote
Originally posted by crazyd: The engine is only pulled from 93-95 Camarobirds, no '96s nor any other vehicles.
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01:31 PM
PFF
System Bot
Blacktree Member
Posts: 20770 From: Central Florida Registered: Dec 2001
I see some misinformation in here, from the usual suspects. But there is some good info, too. Let me make a synopsis.
First of all, the 3.4 TDC (aka LQ1) shares very few common parts with other GM 60-degree V6's, even though it's part of that engine family. The engine uses four camshafts (two in each cylinder head), with four valves per cylinder, to improve the top-end performance. Peak torque is only mildly better than the 3.4 pushrod engine from the F-bodies, but HP is noticeably better, thanks to stronger top-end performance. Since it is built for FWD cars, the starter doesn't need to be relocated.
Power and torque of the LQ1 are rated at around 200-210 HP @ 5200 RPM (depending on application), and about 215 ft-lb @ 4000 RPM.
The 3.4 Pushrod (aka L32) was the final evolution of the iron-head 60-degree V6. It's basically a bored-out 3.1 (which in turn is a 2.8 with a stroker crank), with a few technological improvements (improved oiling, stronger block webbing, internally balanced crankshaft, etc) and an "ear" added to the right side for mounting the starter motor in a RWD car. This engine was used exclusively in the 1993-95 F-bodies. It is also available from GM as a crate engine. Installing this engine in a Fiero is relatively simple, since it's basically just an upsized 2.8 V6. You can take all the "goodies" from your old 2.8 (engine mounts, distributer, intake, exhaust, timing cover, water pump, oil pan, starter, belt-driven accessories, etc) and install them on the 3.4, if you so choose.
Power and torque of the L32 are rated at around 160 HP @ 4600 RPM, and about 200 ft-lb @ 3600 RPM.
The 3400 SFI (aka LA1) is also a pushrod engine, but uses aluminum cylinder heads and sequential fuel injection (hence the SFI designation). Even though it is a pushrod engine, it does not share much in common with the older iron-head engines. So it requires more work to install than the L32. Also note that this engine is the lightest of the three, thanks to the aluminum cylinder heads and single camshaft. This engine is also built for FWD cars, so the starter does not need to be relocated.
Power and torque of the LA1 are rated at 170-185 HP (depending on application) and around 210 ft-lb.
As you can see, the 3.4 TDC out-performs the 3.4 Pushrod. But that performance comes at a cost. The engine is heavier, and is more difficult to install in a Fiero. And since the 3.4 TDC is an "oddball" engine, there is very little aftermarket support. Although, if you're an "RPM junkie", it'll probably be worth it. The 3400 SFI might be a good option for someone who wants more performance than the iron-head 3.4 provides, but doesn't want the added bulk or weight of quad cams.
Also note that all three of these engines will bolt up to a stock Fiero transmission, with no adapter. And all three have internally balanced crankshafts, which means you'll need a neutral-balance flywheel (ala '88 Fiero V6).
[This message has been edited by Blacktree (edited 11-02-2009).]
I was under the impression the 3400 was basically a drop in except for trans mounts (for 4spd 4t60x). The power steering removed and belt/accesory routing altered?
*to clarify,i'm not referring to any wiring-only mechanical,bolt up hard parts.
Things that need to be cut,welded etc..
[This message has been edited by DefEddie (edited 11-02-2009).]
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02:43 PM
ltlfrari Member
Posts: 5356 From: Wake Forest,NC,USA Registered: Jan 2002
Originally posted by Blacktree: I see some misinformation in here, from the usual suspects. But there is some good info, too.
Blacktree, to clarify matters, I certainly hope that I'm one of those providing the latter, as opposed to one of the "usual suspects" you'd referenced, because unless I've overlooked something, I stick with the statements I made in my previous post.
Blacktree nailed all the facts. The difference between the 3.4 L32 and the 3400 engines causes no end of confusion and I am constantly answering questions from people inquiring about this swap if the L32 is in any other cars. The answer is always NO. DefEddie, I don't care what your impressions are, the 3400 is a completely different engine and is NOT a drop-in replacement like the L32 is, and this is the sort of misinformation that gets perpetuated and confuses people trying to figure all this out.
The LQ1 block is also very different from the other 60 degree blocks. It is an adaptation of the 60-degree family block, but good luck trying to use it on your pushrod engine. The valley is completely different and it has no provision for lifters, among many other things. The only things that are the same are the crankshaft and the connecting rods. It is a reliable motor, but it has higher maintenance requirements than its pushrod brethren because of its timing belt. Its less-than-stellar reputation has come about because people treat it like a pushrod motor and neglect it, then scream and call it a piece of junk when it breaks. No, you're just an ID10T for not RTFMing. It is technically non-interference, but a broken timing belt can have other consequences. When 60,000 miles go by, replace it. It's not difficult in its native habitat, but turned around in a Fiero the job requires that you at least pivot the cradle out of the car, if not entirely remove the engine. 60,000 miles is a good five or six years for most people, so it isn't that big a deal.
From a driving perspective, I can't say enough good things about the DOHC. This was the engine that the Fiero was born to have. It revs to seven grand and makes a glorious exotic noise the whole way. The torque curve builds progressively and it is buttery smooth. Mated to the Getrag 282 5-speed, it makes those gears that seem short on the stock engine a whole lot longer.
Unfortunately it's one of the more difficult swaps and there isn't much expertise on it. Most shops won't even touch a W-body with a DOHC, much less a Fiero, so you'll be on your own. But the motor is an engineering marvel when you see how it works, and a joy to drive.
I took over the dohcfiero.com domain when it was abandoned, and most of the information you'll need to do the conversion is there, contributed by fellow PFF members like ltlfrari.
DefEddie, I don't care what your impressions are, the 3400 is a completely different engine and is NOT a drop-in replacement like the L32 is, and this is the sort of misinformation that gets perpetuated and confuses people trying to figure all this out.
Slow down turbo,I wasn't giving any information. I was giving the impression I got from doing numerous searching on here,and fishing for clarification on it. I do know about alot of the numerous differences between 3.4 and 3400,it would be like comparing a 3.8 and a 3800-just ain't the same.
I think I mostly typed out of context,let me try to be more specific. What I consider drop-in,isn't someone else's consideration of drop-in.
"If I don't have to reweld some mounts,and it will bolt to the old ones it is drop-in"
I was under the impression the 3400 engine mounts were in same place as the 2.8/3.1/3.4 blocks were and the engine would basically bolt right up without rewelding mounts (disregarding trans,axles etc...) Still unclear on this,Crazyd you seem to be the authority on it so I would appreciate some clarification on it.
Just because an engine bolts to the transmission and the stock mounts doesn't make it an easy swap or a drop-in. You've still got things like ECM harness rewiring, coolant lines, fuel lines, intake routing, exhaust routing, A/C manifold lines, power steering bypass, alternator rewiring, dogbone mounting, and then all the interference with the factory packaging of the engine compartment like the decklid, strut towers, and frame rails. It is the fact that the 3.4 L32 requires changes to NONE of these things that actually makes it a drop-in - and the 3400 and LQ1 far from it.
Just because an engine bolts to the transmission and the stock mounts doesn't make it an easy swap or a drop-in. You've still got things like ECM harness rewiring, coolant lines, fuel lines, intake routing, exhaust routing, A/C manifold lines, power steering bypass, alternator rewiring, dogbone mounting, and then all the interference with the factory packaging of the engine compartment like the decklid, strut towers, and frame rails. It is the fact that the 3.4 L32 requires changes to NONE of these things that actually makes it a drop-in - and the 3400 and LQ1 far from it.
For ME,if a GM engine bolts in then I consider it drop in. (like I mentioned above.) As mentioned in the above post (did you read it?) I just want to know if the actual motor mounts drop in. The rest is childs play for me,I just don't like to weld or align new mounts. (and a welder is one of the few tools I'm not equipped with at my home shop).
Once again,
If I were to sit a 3400 series engine on my cradle,will it simply bolt on to the stock motor mounts.
3.4 is easiest but retains those horrbile cast iron heads that limit potential. If all you want is a boost in torque and a bit extra power, this is the easiest.
The alloy headed 3400 is a much better engine as far as flow and tuning potential, with a bit more power and torque to start off whther you end up tuning it more or not.
The LQ1 is a very interesting engine. Personally I wouldn't go to all the fuss to put a stock one in - not when you can get similar power from an alloy head pushrod. BUT if you whack a turbo on an LQ1 (more $$) you get to the 300 BHP range with nothing done to the engine internally. That makes it an interesting, if expensive alternative.
Thanks much,I certainly appreciate the info. I can get by the dogbone,that is some welding I can do. (We have welders at my dealership,I just didn't want to swap anything here)
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09:37 AM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
Fiero engine swaps are best done by yourself, or failing that, by the handful of vendors that specialize in a particular range of swaps. It's also a crash course in the car that will be invaluable to you when problems arise.
This is something I failed to consider when I paid someone to do my swap...if something goes wrong, you won't know how to fix it. And the only person that does is the person who did your swap. You will be dependent on that person for the rest of the life of the car. Better to learn how to do it yourself so that you can troubleshoot it and fix it when something breaks.
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09:58 AM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
This engine was used exclusively in the 1993-95 F-bodies. It is also available from GM as a crate engine. Installing this engine in a Fiero is relatively simple, since it's basically just an upsized 2.8 V6. You can take all the "goodies" from your old 2.8 (engine mounts, distributer, intake, exhaust, timing cover, water pump, oil pan, starter, belt-driven accessories, etc) and install them on the 3.4, if you so choose.
Is this still true? I was looking the other day and couldn't find one still new in the crate. I would love to replace my tired old non-running 2.8 with a new crate motor that still looks like a stock engine.
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10:09 AM
lou_dias Member
Posts: 5356 From: Warwick, RI Registered: Jun 2000
Originally posted by jscott1: Is this still true? I was looking the other day and couldn't find one still new in the crate. I would love to replace my tired old non-running 2.8 with a new crate motor that still looks like a stock engine.
It's still available as a crate engine, if that's what you're asking. I bought and installed one earlier this summer. I ordered it from GM Parts Direct for about $2200 shipped, which was the lowest price I could find.
quote
Originally posted by project34: I certainly hope that I'm one of those providing the latter, as opposed to one of the "usual suspects" you'd referenced...
But of course!
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12:04 PM
jscott1 Member
Posts: 21676 From: Houston, TX , USA Registered: Dec 2001
It's still available as a crate engine, if that's what you're asking. I bought and installed one earlier this summer. I ordered it from GM Parts Direct for about $2200 shipped, which was the lowest price I could find.
Yes, that is what I was asking...I guess I didn't search the parts direct catalog properly. Once my GT is smog exempt I would love to drop in a crate motor. Not for the power, just for the reliability. So everything from the Fiero motor bolts right onto that block?
[This message has been edited by jscott1 (edited 11-03-2009).]
I've passed emissions with my 3.4 in 3 different states, though TX wasn't one of them. As long as you can pass with your 2.8, and you tell them that it's a 3.4 at the testing station, you should be fine. Yes, everything from the 2.8 bolts straight onto it with the exception of the A/C compressor bracket, which you'll need to buy or adapt.
[This message has been edited by crazyd (edited 11-03-2009).]
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12:28 PM
lou_dias Member
Posts: 5356 From: Warwick, RI Registered: Jun 2000
Thanks, I need to bookmark your thread...but your engine work is way beyond my capabilities. I just want a new motor that looks like an old motor.
Well, you just send the 3400 to a machine shop and tell them what pistons to use for the rebuild. Other than that it's just rockers and pushrods. Then plugging the hole in the timing cover... You don't actually have to do any of the performance mods I did...
