What's the major differences in these engines? Is the TDC a 60Degree GM? Will any compnents intercharge? Exhaust?

From what I know these engines are very different. The TDC is a dohc 24 valve engine and the pushrod is a ohv 12 valve engine. I dont think ANY of the parts are interchangable. I would go with the pushrod engine. Their are some guys on here with some pertty impresive numbers with that engine. The TDC fromw waht I know is very hard to install.

They are both 60* V-6s. Some of the internal parts can be swapped around. Pistons, cranks, rods. Maybe. I don't think they're identical, but close enough to "experiment" with.
That's about it.
Garden variety pushrod 3.4 motors will make around 160-180 HP at the crank, in Fiero trim. With a few mods, I think 200+ is not unreasonable. Will just about bolt in, in place of a 2.8. Even looks like a stock Fiero motor when done properly. Uses the Fiero computer and wiring.
The TDC is huge. It's a pain in the a$$ to install. After it's done, you have to drop the cradle just to change the front plugs. Needs it's own (or another) computer. Just harder to do.
The "up" side? Hell of a "wow" factor. Makes at least 210 HP, out of the box. Just intake manifold mods can yield impressive horsepower numbers (at the expense of low end torque). Stratospheric redline. Sounds more like a Ferrari than any other powerplant other than a Northstar.

I'm sure others can add to (correct?) my comments.

------------------
Raydar

From the Department of Redundancy Department.

[This message has been edited by Raydar (edited 11-25-2001).]

You're right. The crank and rods are 3.1L. The blocks and everything else are different.

AFter having done both a DOHC and SC swap, I think the DOHC fits the Fiero personality better.

[This message has been edited by terryk (edited 11-25-2001).]

I have the 3.4 TDC and it is, by far, the most impressive engine that you can cram into a Fiero. Hands down!

The sound alone is worth the swap but the 300+ HP that is EASILY squeezed out of this motor is the icing on the cake.

As for it being a pain to install... Not to bad really. The only real issue is making sure you get a motor/tranny together rather than trying to graft it to the stock transmission. With that, things get real easy. Plus a MUCH smoother, stronger and better geared tranny is a GOOD thing

Sure the plugs are a bit difficult to get to... but, in defence, were they any easier to get to in the Grand Prix?

Also, I totally disagree about the high HP is at the expense of the low end torque. This car has tons of torque. I have no idea why I keep hearing about this supposed torque loss???

Anyway, the pushrod OHV vs. the TDC? No contest. Side by side, identical trim and drivers? TDC all the way, from go to top to stop.

Do be intimidated by all the "stuff" on a TDC and the rumors you hear... you'll quickly leave all that behind in a fury of tire smoke when all is said and done

DKOV -

But how hard is it the mount the DOHC and the tranny in the car. Is it pretty much bolt up beside the starter or is it make new mounting points, stretch the frame.... or what? The 3.4 swap is something that I am interested in and I am just now looking at what engine will fit easier/better so that I can do it myself. Oh and it has to be able to get 12.9 - 12.3 in the 1/4 mile (am I just dreaming on the last part? I am trying to keep up to my brother's 3000GT. God I hope he doesn't get the Supra)

BTW anyone know some good website that have performance parts for either engine?

[This message has been edited by RacinRob (edited 11-26-2001).]

Rob:

The process was pretty straight forward by my recolection. That whole bit about having to swap and special drill the starter is for the OHV pushrod motor, I left everything on my motor as it was.

The motor mounts are new and different but included in the kit I purchased for the swap so the motor and tranny bolted right up onto the K-frame with only one little "cut" to the frame for better clearance. Nothing major.

The Power steering pump is removed or plugged. The kit comes with plugs and you just fill the pump and leave it in place. I chose to completely remove it to lesson the load on the motor and squeeze another pony or two out of it. So I fabricated an Idler pully in its place.

The only real custom swap part I had to deal with was a new torque strut that I had milled from aluminum. It is not absolutely needed but with the power my TDC is putting out, I figured safe than sorry

The wiring harness is from the donor car as well as the Computer but... The ECU is a straight bolt in and work with the Fiero and teh harness you send back to the kit provider and he combined it all to the old Fiero engine harness for me. No work or sweat off my brow!

When it all came back, It all went right on as promised. Of course, it did take about 3 weeks for the harness to go and return, but I spent that time adding more HP to the motor anyway, so no big loss.

The other things to grab from the donor are the axels. You need the tranny side of the axels to mate to the bone side of the fiero axels. They fit right together and it's not a hard job either. Of course, having to source them if you didn't get them with your motor/tranny might be difficult.

Of course, that is also negated if you are using the stock Fiero tranny mated to the TDC.

Beyond that, you get new fuel hosing, new radiator hosing and a speedometer swap (provided with the kit as well). That's it.

Done.

Any motor swap you do will require pulling the K-frame and remounting the motor. In that, the TDC is the very same as any other swap you will ever do. The difference is that it is a BIGGER motor with more wiring so it LOOKS intimidating, but it's really not bad.

Take some advice too... As long as you are "in there", spend the extra bucks and replace wearable parts. I put all new shifter cables and brake lines and plug wires and...

You get the idea. I even went as far as puting new wheel bearings in! Anything you can do NOW will be much easier than in the future when it's all back together

I'm putting together a page on my website that incorporates all the assembly pics, finish pics and fire breathing, tire smoking pics... It'll be us soon

If you need ANY help... just ask!

DKOV -

RacinRob,

The DOHC is a great choice for the Fiero and fits the cradle fine. You do have to cut out part of the right hood hinge and dogbone area. If you have emissions testing, there are a few considerations with the manual trans version (such as an air pump for the exhaust).

But (here come the flames), don't do it expecting to get 300HP out of the engine without blowing on it (turbo/sc). You won't. There is no tuning trick in the ECM/chip to do it and the few people that have gotten 250HP+ will readily admit the car is nearly undriveable. There are no camshafts readily available (there are custom cams at $1000+/set).

Do it expecting 210-230 HP without throwing more money at it. With the manual transmission, you will love it unless you want the heavy torque off the line of a Buick V6's or V8's.

I agree with most of what Terry is saying and I think the differences may be in the company that is providing the conversion kit...

I didn't have to CUT anything except some minor trimming at the right hand hinge. Ultimtely, I did away with the spring/hinge altogether and replace it with Rodney Dickman's strut setup. Much better looking, in my opinion.

The bones cleared just fine with my car. No issues there.

As for the HP hitting 300... I disagree there. Start from 215 and do what everyone does like add a K&N and add... well, you WILL get a custom exhaust, like it or not, when you convert because the stock system will NOT mate back up.

Those two things alone will give you 230ish... Some Valve grinding, intake plenum work, throttle body work, underdrive pulley, fuel delivery, etc... 300 HP is NOT unattainable BEFORE you blow the motor with a Turbo or Super Charger.

I DO agree that at the 300 mark, the car is VERY fast and a bit of a monster, but that's the POINT right? It WILL rip your head off!!!

As a direct comparison, my Lotus Esprit Turbo has around 300 HP and does 0-60 in 4-4 seconds and 0-100 in 9.8 seconds. These cars are about the same weight and the seat-o-the-pants-o-meter says they are doing about the same although I have yet to dyno the Fiero.

I would not even bother charging it in any way... That would be to much for both the driver and the drive line, I think.

In any case, you will get more out of a TDC at BONE STOCK trim than you will with a Push-rod motor with most NA mods.

Of course, there is the SOUND that you cannot get with ANY other motor

DKOV -

I will make a free 3.4L DOHC chip (9396 ECM only) set to any calibrations you want if someone emails me a real 3.4L DOHC normally aspirated dyno chart showing 300HP or better at under 7000 RPM.

You are free to use the generous multiplier of 17% for drivetrain loss. The engine must have started as a production engine. Don't try sending me a dyno chart from a GM prototype car. Make whatever changes you want except for boosting the engine or nitrous. Run race gas if you like.

Oh, the sound. The 3.4L DOHC is worth it JUST for the sound!

[This message has been edited by terryk (edited 11-26-2001).]

After rebuilding motors in the past,trying to make all sorts of aftermarket JUNK work,making my own parts,drilling out rusty/broken bolts,I decided to go with a stock,late model,low mile TDC motor.I even use a stock clutch.
I layed it all down in a recent thread about this same topic here on the forum.
After it was installed and running,I added underdrive pulleys,an electronic air/fuel controller(intercepts airflow signal and tweaks it),and a larger aircleaner.I would guess that I get around 240hp,maybe.
Something else to keep in mind is that with the later model motor,you're getting newer accessories as well;the starter is a different type,the alternator is a tech-looking unit,most likely you'd get an A/C pump too,all the sensors(I even have knock sensors),newer injectors,and those sparkplugs that you can't get at don't need changing for nearly 100K,so who cares!
I appreciate the original type motors as well,but I don't have the time anymore to mess around that much either.
That's one great offer by Terry on the ecm tune-up too!

Terry...

I'd take that offer but I don't think you can build a chip for a 3.4 TDC mated to a factory 5-speed. At least, GM says they can't.

Anyway, figuring by Math, I may have around 280 ish at the wheels, but as I said before, I'll get some dyno work done and go from there.

All I know is that it is WAY to fast

Sounds like you know

DKOV -

Do they still make the 3.4TDC? If not what's the last year they produced it? Also what cars were they in, I know the Z34 Lumina is one, what else??

quote Originally posted by newfie: Do they still make the 3.4TDC? If not what's the last year they produced it? Also what cars were they in, I know the Z34 Lumina is one, what else??

I got one in my 93' Cutlass Supreme. The last generation Grand Prix GTP had it too. I love the 7000 redline. I got the car from my dad and he said he was able to do 110 in 3rd gear. Some kills include BMW 328, the new maximas, and galant v6. I can eat any NA four banger for breakfast with the exception of the S2000. My next hunt will be the Acura RSX Type S. Oh YEEAAA. I beleive the last year they made this engine was 96'.

[This message has been edited by Cutlass207TDC (edited 11-26-2001).]

I'm not really sure which year, but the changed the name from Dual Twin Can to Dual Overhead Cam for reasons unknown.

I think, in fact, that the 3.4L DOHC of today is the same basic engine design.

Both are 24 valve.

DKOV -

That's why I said the 9396 ECM only. It supports the manual trans (especially important since GM shipped a lot of DOHC's with manual transmissions). I haven't worked on the 6401 much and it doesn't support the manual trans. I haven't done any work on the flash PCM and don't plan on it.

The offer stands. Manual or automatic. I don't see a 94 and up 6401 or flash engine making 300 HP NA either without some very hefty money poured into it.

[This message has been edited by terryk (edited 11-26-2001).]

As someone who has put a ton of research into this engine as well as extensive conversation with master ASE tech "Joel", last name omitted, author of the infamous 270hp TDC/DOHC detuned engine article, I have to agree with TerryK.

"Theoretically", the engine flows well enough to make approx 310hp, especially the '96 and '97 model DOHC, albeit it would drive like a NSX without the low end VTEC, and it would take a LARGE investment. Specifically:

Cams: gotta have more duration if you want this engine to sing in the upper rpm band ~$1000

Intake manifold: Micheal Smith in CA, see www.fiero.cc, made a large "intake sump" and replaced the long, "ala torque maintaining" intake runners. Yes this opened up the top end but took a bit from the mid-range and made the car very quirky and difficult to drive. So a "tuned" intake runner intake is a necessity.
~$500 simple sump to ~$$$$$$ for a custom made tuned runner system.

Valve Springs: There is more hp above 7500 rev limit but the springs will seriously float at ~8000.
~$500 - $1000 for custom wound 60 - 100lb springs.

And finally to really eek out the last hp's you'd probably have to go with a standalone EMS. The GM6401 ECM could probably be used if it was re-programed for a manual and the fuel/air maps reset for a much greater flow, but in the end a standalone would probably be cheaper, e.g. Haltech E6K or Autronic SM2.
~$1000 - $2000 sans installation and tuning.

The '96 and '97 DOHC engines have slightly redesigned better flowing heads and exhaust manifold ports along with a SFI ECU, but alas the ECU is for auto's only, and it isn't as torquey down low as the earlier models.

I've also looked into retrofitting a the dual runner flapper valve setup from a taurus SHO v6 or even a TVIS setup from a mr2 turbo to keep the low end torque. You don't even wanna go there. $$$$

I've seriously considered turbo charging the engine, and still am even as I'm trying to sell my DOHC and Fiero, with lower CP forged pistons, o-ringed heads, and metal hg's with a BB Garrett GT30 or GT35 and air/water intercooler. The flow numbers of this engine are ubelievable and a turbo'd intercooled version could really hit some impressive numbers, and I stress "impressive" with moderate psi levels. If the internals could be strengthened to take the boost, then hello modded Toyota Supra TT ET's but better due to the larger displacement 3.4 vs 3.0 and mid-engine fiero layout. We're talking 500hp on 15-20psi of boost. Eat your heart out V8 fieros. JK

Problems with turbo'ing it:
Engine heads are HUGE, very little room for much else in there.
Plumbing - custom made $$$$ cha-ching!!
Turbo - New Garrett BBT4 or GT30 $2K
Intercooler setup - no apparent room for air/air so spearco air/water, pump, resevoir, heat exchanger - $1200 - $2000.
WasteGate, Blow off valve, fittings, lines - $1200.

How much do you want to spend on a 15 year old car? In the end, you'd spend just about as much for a quality hi-po archie conversion with one helluva wow factor.

Sorry for going on so long. I just hate to see people start thinking this engine can just be "tweaked" into making 280-300hp. It can't, plain and simple. The engine has "enormous" potential but it will cost big $$$$, just as any big hp setup will.

I've often thought that if one wanted low end grunt with a turbo upper end then do a Syclone Turbo 4.3L V6 with an archie kit. All the parts are in GM's parts bin and readily available and the engine is made for turbo'ing.

GM also wants the 3.4DOHC engine to go away. The VIN even has an "X" in it. And price for parts for this engine are on par with import tuner prices.

IMHO, It has the potential to be the ultimate fiero engine. Decent low end, screaming redline, relatively low weight, and almost unlimited turbo'ing potential. But at a cost.

Thanks for you time,

Sincerely,
msweldon

A final note on the exhaust. On the 91-95 engines, you can take a front manifold and flip it over on the back. Have a Fiero style crossover pipe made and it will bolt to the stock fiero exhaust system. That is what we did on the 85 GT DOHC for sale in the mall.

TK

Terry:

I never thought of flipping the manifold! Great idea... Too late for me though

Oh, check this thread...
https://www.fiero.nl/forum/Forum2/HTML/015826.html

Pretty interesting.

DKOV -

Yep, that about covers it.