2.8 vs 3.4 (Page 1/2)
sledcaddie JUL 25, 10:28 AM
I've had several people say they swapped to a 3.4. Only difference is the starter is relocated to opposite side. Same wiring harness? What is the advantage of the 3.4? How much more power/torque does it have? Is it just a larger bore or stroke? Any other major differences? Thanks for all responses.
olejoedad JUL 25, 11:26 AM
Larger bore and stroke.
Better oiling than the 2.8.
Accepts the Fiero lower, middle and upper intake.
Same wiring harness.
More torque and horsepower - you can feel the difference.
cvxjet JUL 25, 12:00 PM
I have done this swap- More HP and a lot more torque- and it's at a lower RPM...Basically like swapping in better gear ratio.

My 1985 SE V6 (No other options- so light at 2580) 0-60 = 7.5, 1/4 = 15.5

Swapped 3.4 and Getrag 5 speed; 0-60 = 6.5, 1/4 = 14.8

As far as fuel efficiency, Originally I got 22/28 mpg.....Now, I get 20/30.

The acceleration numbers come from a G-meter....Crossing the San Mateo bridge at 5 am going to work (No traffic, board flat and straight for 5 miles)

I like it because it also looks stock- I liked the way the Fiero V6 looked....

[This message has been edited by cvxjet (edited 07-25-2023).]

fierofool JUL 25, 06:16 PM
Aside from the aforementioned starter relocation, you will need a neutrally balanced flywheel and 17# injectors. I used a 3.1 Beretta flywheel.

The 2.8 injectors don't flow enough fuel and it will run extremely lean. Finding 17# injectors that run efficiently on the stock ECM seems to be a bit of a problem. At least that was my experience with three 3.4 swaps. I finally got the 3rd one sorted out by doing the 1227730 ECM conversion and using injectors that didn't work with the stock ECM.
sledcaddie JUL 25, 10:40 PM
The above information is helpful. Knowing about the injector size and the balancer could make or break the engine's performance. Thank you.

What I was looking for is actual numbers from each engine for a side by side comparison.
For example:

2.8 V6 - 135 hp.

3.4 V6 - ??? hp

3.8 Supercharged V6 - ??? hp.
Raydar JUL 25, 11:24 PM
The 3.4 is rated at ~160 HP in the Camarobird. But the real difference is in the torque. As previously mentioned, it makes a lot more torque, down lower in the rev band. It really feels like the engine that should have come in the Fiero.
You can coax more out of it, but it gets spendy. The first things to do would be to port the exhaust manifolds and mod the upper intake plenum, on the underside of the neck.
(Look for the "Dawg" intake mod.) A larger throttle body will also help. Those things are the major "choke" points.

I built a 3.4 a while back. It felt almost as strong as my 4.9, but it was expensive. I had ~$700-800 just in head work (including reconditioning and porting.)
I also had a lumpy cam, tuned headers, and 19# injectors, along with a Trueleo intake.
It was ugly as sin, but based upon other peoples' builds and results, I'm guessing it was ~200 HP.

As always, YMMV.
olejoedad JUL 26, 06:30 AM
Torque is much more important than horsepower.

Think of it this way.....torque is acceleration, horsepower is top end speed.

Having both is better, if you want that, go for an LS swap.
shemdogg JUL 26, 09:16 AM
3.8sc puts out 240hp, I think the NA version is 200hp. Both are obd2

shem
olejoedad JUL 26, 11:07 AM
The 4.9 Cadillac motor is a good swap as well.
Gobs of torque immediately when you push on the gas, and lightweight.
No waiting for the supercharger to build power, and no annoying whine.
And the V-8 exhaust sound.
A_Lonely_Potato JUL 28, 08:34 PM
for what its worth, heres the power curves of a 3.4 camaro and a fiero GT overlayed. i know there are different losses given the transmission and axle setups, but its ballpark.



(the 2 upper lines are the 3.4...obviously)