Hi everyone,

I'm smack dab in the middle of a 3.4L PR swap on my 88GT and I'm wondering if it's worth the added effort to replace the stock Torque Converter in the Auto TH-125 trans while everything is apart? I already ordered up a TransGo Shift Kit and the 3.4 that is going in has a new 272 CAM...

Any suggestions guys?

Thanks!

I did that swap, I did not change the converter. The 3.4 already HAS more torque, in my opinion all you'll accomplish is generating More HEAT & worse fuel economy. You're Not building a "RACE Car". just flush the converter you have to get rid of the old fluid. (1/8" hole drilled at 1 of the "Lugs", drain it, then some epoxy on a "Blind" 1/8" rivet, put in a Qt of Clean fluid, & re-install. just my 2 cents.

Thanks for responding Lou6t4gto!

And thank you for your insight on this swap! This is my first swap ever... and I don't want to miss something that'll cost me down the road. I've read in other posts that people have swapped torque converters out from Duke trans and used them on the 2.8s with good results. But couldn't find much on this regarding the 3.4PR...

quote Originally posted by 1Shamrock: I'm smack dab in the middle of a 3.4L PR swap on my 88GT and I'm wondering if it's worth the added effort to replace the stock Torque Converter in the Auto TH-125 trans while everything is apart? I already ordered up a TransGo Shift Kit and the 3.4 that is going in has a new 272 CAM...

quote Originally posted by Lou6t4gto: I did that swap, I did not change the converter. The 3.4 already HAS more torque, in my opinion all you'll accomplish is generating More HEAT & worse fuel economy. You're Not building a "RACE Car". just flush the converter you have to get rid of the old fluid. (1/8" hole drilled at 1 of the "Lugs", drain it, then some epoxy on a "Blind" 1/8" rivet, put in a Qt of Clean fluid, & re-install. just my 2 cents.

I think Lou6t4gto actually used the stock 3.4L cam in hs engine swap, and I'd agree with him that combination already provides plenty of low-end torque, obviating any need for a special torque converter.

However, 1Shamrock, I belatedly noticed in your first post above, this comment:

quote Originally posted by 1Shamrock: ...the 3.4 that is going in has a new 272 CAM....

I assume you're referring to the Crane H-272-2 cam.

If so, your torque converter question seems a less cut-and-dried issue, and makes more sense to me because the stock 3.4L cam versus the aftermarket Crane H-272-2 cam are considerably different in their lift and duration specifications. Therefore, let's not inadvertently overlook the distinction between the two in your situation, especially given that your Fiero is equipped with an automatic transmission (a transmission normally less well-suited to a camshaft which is targeting the production of a higher-RPM power band).

As you very likely know already, it's not unusual to employ a higher-stall converter to compensate for the typically lesser off-the-line torque afforded by some aftermarket cams.

Accordingly, for your purposes, I'd like to kow if anyone here successfully has completed a pushrod 3.4L engine swap for a Fiero actually equipped with...

• a Crane H-272-2 cam,
  
• a TH-125 automatic transmission like yours, and if so,
  
• how did they handle your torque converter issue with that particular camshaft and transmission combination?

If we see no response to that inquiry, and if you still feel you need a new aftermarket cam in your 3.4L engine swap right now, then I'd recommend going instead with the somewhat milder, Crane H-260-2 cam, instead of the Crane H-272-2 cam you've mentioned. The H-260-2 is less likely than the H-272-2 to require special electronic tuning, would be more well-suited to an automatic-equipped Fiero, and shouldn't require any consideration of installing a special torque converter.

Incidentally, welcome to Pennock's Fiero Forum.

I'll second that

Thanks project34!

I really hope that someone has taken on a similar build. I'm actually past the point of no return since the new 272 Cam is already installed.
I was actually hoping to squeak by without having to replace the Cam in the 3.4 but with 80K on it already, the old Cam was pretty well worn out.

You mentioned that the H-272-2 may require special electronic tuning as well... Would this hold true with a 7730, because as we speak the guys at the shop are cutting and tracing wires to install that as well?

When I started on this path to do the swap I just wanted to have it done right...but now I'm scared...
HELP!

Thanks again everybody for all of your insight into this... and thanks for welcoming another Fiero Owner to the Forum!!!

I'd just leave the stock torque convertor. I'm running a turbo 3.4L with TH125c and it drives just fine.

Are you rebuilding the trans? If yes then go with a new/reman stock stall speed unit. If no then install the old one. Are you planning on a dedicated racer? If yes then a higher stall speed TC is for you. This gets the rpms up higher into the power band for launch. If not a dedicated racer then stick with the stock stall speed.

The choices I see are stock stall speed vs higher stall speed and new/reman vs original. How are you going to use the car?

quote Originally posted by 1Shamrock: You mentioned that the H-272-2 may require special electronic tuning as well... Would this hold true with a 7730, because as we speak the guys at the shop are cutting and tracing wires to install that as well?

Yes.

The -7730 ECM swap by itself doesn't automatically rectify all the adverse consequences on streetability that are created by installing, for example, a camshaft or injectors that are sized too large for your Fiero's primary intended usage.

Instead, think of the -7730 ECM swap simply as permitting more extensive and better electronic tuning capabilities than would your Fiero's original ECM.

quote Originally posted by Hudini: I'd just leave the stock torque convertor. I'm running a turbo 3.4L with TH125c and it drives just fine. Are you rebuilding the trans? If yes then go with a new/reman stock stall speed unit. If no then install the old one. Are you planning on a dedicated racer? If yes then a higher stall speed TC is for you. This gets the rpms up higher into the power band for launch. If not a dedicated racer then stick with the stock stall speed. The choices I see are stock stall speed vs higher stall speed and new/reman vs original. How are you going to use the car?

Thanks for responding Hudini!

It's reassuring to know that someone has had luck with their TH125 Auto!
Are you also using 272 Cam?

I'm using the Comp Cams 260H because of the even duration and wider lobe separation angle. The Crane H-272-2 is more for a normally aspirated engine. It should have a nice lope to the idle.

I'm also running the 7730 and DIS from the 3.4L engine. For tuning I'm using code59 as it allows a wide-band O2 input and a 3-bar map sensor for up to 30lbs of boost. I bought the APU1 from Moates and hooked it to a laptop running TunerPro RT so I can tune on the fly.

You will not have any issues with your cam and trans for a normal street car. Plus I don't think you can make enough torque to trash it either. Now add a turbo and intercooler then crank up the boost and, well, you'll need a rebuild. Guess how I know

quote Originally posted by Hudini: I'm using the Comp Cams 260H because of the even duration and wider lobe separation angle. The Crane H-272-2 is more for a normally aspirated engine. It should have a nice lope to the idle. I'm also running the 7730 and DIS from the 3.4L engine. For tuning I'm using code59 as it allows a wide-band O2 input and a 3-bar map sensor for up to 30lbs of boost. I bought the APU1 from Moates and hooked it to a laptop running TunerPro RT so I can tune on the fly. You will not have any issues with your cam and trans for a normal street car. Plus I don't think you can make enough torque to trash it either. Now add a turbo and intercooler then crank up the boost and, well, you'll need a rebuild. Guess how I know

Hi Hudini!
Thanks for reassuring me that my cam/trans combo will work well... I was starting to panic! And yes, this is strictly a street car with an occasional traffic light fun... I don't think I'll be going the turbo route and if I did I surely wouldn't try for 30lbs of BOOST! But I can imagine that it would be fun!... So, why did you need a rebuild?... jk...

At the most, I'd consider a DTB from Street Solutions or a Trueleo somewhere in my future (if the price is right or if a member would like to donate to my cause... ). I'll check out Moates for sure, and try to become more familiar with the whole tuning process.

From where I sit now, I guess I'm going to keep the stock Torque Converter and press on with the build!

If anyone has any suggestions or ideas on anything that could help my build please respond...

Thanks again!

quote Originally posted by 1Shamrock: If anyone has any suggestions or ideas on anything that could help my build please respond...

I'll attempt to cover several areas here, starting with injectors:

quote Originally posted by 1Shamrock: As far as injectors are concerned, I'm looking to use the stock ones for the 3.4PR (17# I think).

Yes, the stock size of injectors for the pushrod 3.4L V6 engines (found in `93 through `95 V6 Camaros and Firebirds) is indeed 17 pounds, and that is all that is needed for your 3.4L engine's current setup.

If your Fiero's 3.4L engine is normally aspirated, it likely won't be necessary to go to injectors larger than the stock 17-pound size until meaningful parts modifications or substitutions are made in all of the following areas, which in turn will permit the engine to realize its performance potential with the H-272-2 cam:

• Some Suggested Parts Modifications/Substitutions with the H-272-2 Cam in a Pushrod 3.4L
  
• ...Intake Manifold (e.g., Trueleo for EFI, or Edelbrock for carburetion)
  
• ...Throttle Body (e.g., pofessionally bored out stocker, or different and larger throttle body model)
  
• ...Headers (e.g., Trueleo or Sprint headers)
  
• ...Y-Pipe (e.g., Trueleo or Fiero Store or ported)
  
• ...Cylinder Heads (e.g., professionally ported and shaved)

quote Originally posted by 1Shamrock: Do you still think I'm going to have trouble with the CAM/Trans combo in terms of performance? Is there anything I'm missing?

"Trouble" may be an overstatement. However, some disappointment seems likely until changes like those I've listed above are made to permit your 3.4L engine to realize its performance potential with the H-272-2 cam. With the modifications you've listed so far, my concern is that the H-272-2 camshaft and the remainder of the engine are not yet particularly well-matched.

If you will invest the time, effort, and money to do that well, I suggest sticking with the H-272-2 cam. If not, I suggest switching to a milder cam.

For example, let's revisit two modifications you've mentioned earlier here in your thread:

quote Originally posted by 1Shamrock: ...I have a larger Throttle Body with a ported intake....

Counterintuitive as it may sound, those two modifications aren't likely to help your 3.4L engine swap much, if at all --- at least not yet.

Why not?

The factory cast the V6 Fiero's intake manifold with a crimped neck (not entirely dissimilar from the crimp in the stock Fiero V6 exhaust's Y-pipe, which sometimes is called a crossover pipe). The crimp in the neck of the Fiero V6 intake manifold doesn't do anything good for a larger throttle body or a ported intake. This limitation is illustrated nicely in photos PFF member, triker, once took of a cut open, Fiero V6 intake manifold (first photo below), overlaid with a gasket for a Fiero V6 throttle body that had been bored out from the stocker's 52mm diameter to 57mm (roughly 20% larger in area):




Now that second photo in particular is an eye-opener, isn't it?

Unanticipated or otherwise hidden complications like that are one reason why I suggest that if you decide to invest the time, effort, and money to match the remainder of your 3.4L engine's components well with its H-272-2 cam, then I suggest sticking with that cam, but if not, I suggest switching to a milder cam.

Whatever you end up deciding to do, I hope the suggestions I've outlined in this thread will help you out with your 3.4L engine swap project.

Thanks for the information and suggestions Project34!
You're an awesome resource on here and I really appreciate your help!

There's just no getting around that intake is there? Why oh why did the boys over at Pontiac design it like this? I'm not a gear head by any means and after looking at that photo, I have to say it's a definite red flag!

Chances are that I'm going to take a trip out to Bemidji, MN (about 2 hours from where I live) this fall and invest in one of their DTB Performance Intake Manifolds. Unless, sometime this summer I happen to stumble across a great deal on a Truleo on here...

quote Some Suggested Parts Modifications/Substitutions with the H-272-2 Cam in a Pushrod 3.4L ...Intake Manifold (e.g., Trueleo for EFI, or Edelbrock for carburetion) ...Throttle Body (e.g., pofessionally bored out stocker, or different and larger throttle body model) ...Headers (e.g., Trueleo or Sprint headers) ...Y-Pipe (e.g., Trueleo or Fiero Store or ported) ...Cylinder Heads (e.g., professionally ported and shaved)

Thanks so much for the suggestions listed above!!!

And here's where I'm at...

... Intake Manifold (Ported stock... half way there - But I'm looking for something better)
... Throttle Body (Check)
... Headers (WCF Logs - Better than stock, again I'm looking)
... Y-Pipe (Check)
... Cylinder Heads (Not too sure about this one? I had the heads redone. Does that count? Maybe some more information here would help... )

Thanks again Project34 and to everyone else here that has offered their insight!

quote Originally posted by 1Shamrock: There's just no getting around that intake is there?

Not easily with the stock Fiero V6 intake manifold, no --- and not easily even with a somewhat modified Fiero intake manifold.

For example, although I've not seen any posts from him lately, PFF member Dawg once offered a Fiero intake manifold which he rewelded to eliminate the crimp in the neck of the stock Fiero intake manifold, something which porting a Fiero intake manifold doesn't do. However, as is the case with a ported intake manifold like the one you've purchased, rewelding to eliminate the crimp in the neck of a stock Fiero intake manifold still doesn't shorten the overly lengthy, sharply bent runners of a Fiero intake manifold. In turn, and unfortunately for your H-272-2 cam which favors power production at higher RPMs than would a milder or stock cam, longer runners typically favor power production at lower RPMs, whereas shorter runners typically favor power production at higher RPMs.

quote Originally posted by 1Shamrock: Why oh why did the boys over at Pontiac design it like this?

GM most assuredly has the intellectual resources to be able to design a higher-performance intake manifold. However, in this case, the Fiero intake manifold's design appears to have been compromised by the cost-cutting goal of designing the basic intake manifold to fit within a plethora of very different cars --- not just Fieros --- and also with an emphasis on around-town, off-the-line torque. In turn, an emphasis on around-town, off-the-line torque typically favors longer intake manifold runners, not the shorter runners which typically favor performance at higher RPMs, and which in turn would be better matched with your H-272-2 cam.

quote Originally posted by 1Shamrock: Chances are that I'm going to take a trip out to Bemidji, MN (about 2 hours from where I live) this fall and invest in one of their DTB Performance Intake Manifolds. Unless, sometime this summer I happen to stumble across a great deal on a Truleo on here...

I very much like the appearance of the TLG/Street Solutions DTB intake manifold. However, before you travel two hours to Bemidji, MN to purchase one, I strongly recommend you do two things:

1. Compare the total price of that TLG/Street Solutions DTB intake manifold that you'd like to get ( http://www.tlg-store.com/Hi...nifold_p/4010104.htm ) with that of a Trueleo ( http://www.trueleo.com/index-old.htm ). Doing so seems likely to surprise you, based on your comment about a "great deal" which I've quoted just above this one.
   
   
2. In the thread titled, "TLG Product Announcements: Cool New Stuff For Your Fiero!", check out the written responses to the "running rich at higher RPMs" questions I raised in my posts of 9-23-2011 ( https://www.fiero.nl/forum/F...1/HTML/086463-3.html ) and 11-25-2011 ( https://www.fiero.nl/forum/F...1/HTML/086463-4.html ).

quote Originally posted by 1Shamrock: And here's where I'm at... ... Cylinder Heads (Not too sure about this one? I had the heads redone. Does that count? Maybe some more information here would help... )

As a substitute for professional porting, "No" is the short answer to your question, "Does that count?"

The basic goal for "redone", rebuilt or remanufactured cylinder heads essentially is to get the cylinder heads back to the same shape they were in when they were new. That, for example, may involve such things as repairing any cylinder head cracks, replacing the valve springs if they're in poor condition, and regrinding the cylinder heads' valves to OEM specifications, or replacing the valves if necessary.

The basic goal for professionally ported heads essentially is to streamline passages within the cylinder heads not just for its own sake, but in order to improve airflow potential within the cylinder heads by a substantial and quantifiable amount.