PFF - Pennock's Fiero Forum, PDA Edition

2.8 weak points? (Page 1/1)

Josh86gt

FEB 17, 01:48 PM

I was just curious as you start adding power to the 2.8 what are the weak points preventing more power I know it's a low displacement engine and I'm not expecting anything over 300 horsepower with boost I'm just trying to do a bit of bulletproofing

1985 Fiero GT

FEB 17, 02:27 PM

Generally from what I've read, a 2.8 will lose a lot of reliability over 200 HP. The bottom end doesn't get enough oil, the rods, crank, pistons are cast and weak, the block is thin and weak in areas, the compression ratio is higher than would be optimal for safe boost, especially with no knock sensor, the heads, intake, and exhaust manifolds don't flow very well.

Porting the intake manifolds and exhaust manifolds, 1.6 ratio roller tipped rockers, full refresh of the ignition system, new sensors, and other well documented things can get it to about 160hp, as other people have dyno-d, I've done those and using my 0-60 time and calculators have gotten an estimated 160hp to, although that's just a guess.

Adding boost to the 2.8 is a very good way to blow it up, most of the "kits" kept the boost very low, and made around 200hp, that is generally the maximum reliable safe level with the 2.8.

Another alternative is to use a different 60* v6 block, with the Fiero top end (or the other top end if you aren't attached to the look), the firebird 3.4 is better than the 2.8, but still not the best, the third Gen 60*v6 (3100, 3400, 3500), are stronger, priority mains oiling (bottom end gets priority), better (and roller) camshaft, cross bolted mains, structural oil pan, more block reinforcement, lower compression ratio when used with the Fiero heads and intake, forged rods (and in some cases crankshafts to I think).

PM Brunelle uses a 3.1l engine in his build (the white bug), I think it's not the 3rd gen block, but the same gen as the firebird 3.4 (I think considered 1.5 gen) with the 3100 pistons, and is running a turbo, water injection, and it is a very well thought out, nice build. I'm doing a turbo 3400 this winter, with inspiration from his build (but won't be as well put together haha)!

Josh86gt

FEB 17, 02:29 PM

quote

Originally posted by 1985 Fiero GT:

Generally from what I've read, a 2.8 will lose a lot of reliability over 200 HP. The bottom end doesn't get enough oil, the rods, crank, pistons are cast and weak, the block is thin and weak in areas, the compression ratio is higher than would be optimal for safe boost, especially with no knock sensor, the heads, intake, and exhaust manifolds don't flow very well.

Porting the intake manifolds and exhaust manifolds, 1.6 ratio roller tipped rockers, full refresh of the ignition system, new sensors, and other well documented things can get it to about 160hp, as other people have dyno-d, I've done those and using my 0-60 time and calculators have gotten an estimated 160hp to, although that's just a guess.

Adding boost to the 2.8 is a very good way to blow it up, most of the "kits" kept the boost very low, and made around 200hp, that is generally the maximum reliable safe level with the 2.8.

Another alternative is to use a different 60* v6 block, with the Fiero top end (or the other top end if you aren't attached to the look), the firebird 3.4 is better than the 2.8, but still not the best, the third Gen 60*v6 (3100, 3400, 3500), are stronger, priority mains oiling (bottom end gets priority), better (and roller) camshaft, cross bolted mains, structural oil pan, more block reinforcement, lower compression ratio when used with the Fiero heads and intake, forged rods (and in some cases crankshafts to I think).

PM Brunelle uses a 3.1l engine in his build (the white bug), I think it's not the 3rd gen block, but the same gen as the firebird 3.4 (I think considered 1.5 gen) with the 3100 pistons, and is running a turbo, water injection, and it is a very well thought out, nice build. I'm doing a turbo 3400 this winter, with inspiration from his build (but won't be as well put together haha)!

Ok thanks I may just buy a 3.4

Dennis LaGrua

FEB 17, 05:48 PM

For all the reasons pointed out in the above post; I believe the magic limit number for reliability in the 2.8L is around 190 HP. At one time I ran a turbo on a stock 2.8L and with 5 psi of boost it held together until the engine was taken out and sold. It was a low mileage engine so maybe that was key. .

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

La fiera

FEB 17, 08:12 PM

At Charlotte chasing a Mitsubishi Conquest Turbo, and I got him.

Stock vs upgraded 2.8L With a different custom intake it made 173whp and 160wtq.

The 2.8L (L44) is a very good engine. The oiling problem can be remedied by using the oil pump from the 3.4L engine. Even though they my be similar to the naked eye they are not. The 3.4L pump has a larger diameter inlet pick up tube and get the Hi-Volume one. Make sure you weld/tack the pick up tube. Take the pump apart and polish the impellers, shafts, floor and roof of the housing to have the pump turn easier. Notice I say "polish" not grind. Also, take off the oil filter bypass valve at the block, all hi quality oil filters have a bypass valve integrated. Don't use cheap oil filters and make sure you don't use 10w-30, use 15w-40 Full Synthetic or higher viscosity. Remember, oil gets thin as it heats up.
Before I went to the 3.4L upgrade, I rebuilt the 2.8L that came originally in my Fiero with some unique upgrades and also made sure the rotating assembly was balanced since I was going to track it a lot.
The only problem I had was a blown harmonic damper because that engine was constantly between 4500 to 6500 rpms during the track days. Invested in a very good damper and what a difference!
I did countless track days for 3-4 years before going to the 3.4L and all I can say is that I had nothing but good memories with it. I still have that block prepped in my garage! You can hear and see the difference between the stock and upgraded engine at the beginning of the video below.
https://www.youtube.com/watch?v=Zo5PwZ5Lohk&t=23s
Sorry, I haven't been able to embed videos yet!

82-T/A [At Work]

FEB 18, 07:35 PM

Only thing I would add to what everyone is saying above, is that on stock 2.8s, the weak point tends to be the crank and rod bearings (oiling issue that La Fiera is talking about). It seems most 2.8 Fieros meet their end because they develop a rod knock. That's what happened to my stock 2.8, failed at 105k miles. It happened because I bought one of those aftermarket Coltec Industries waterpumps with the plastic impeller (never get one with a plastic impeller) and it gave out while on the highway, car overheated like crazy... wore out a main bearing and developed a knock.

I think you've made a couple of posts, but make sure you really plan out what you want to do. If you don't care about keeping the fancy red Fiero intake plenum, then you can pretty much use any V6/60 motor you want, you'll just have to take the ECM and wiring harness with it.

The nice thing about the Fiero gauges is that they operate independently from the ECM. So... unlike modern cars where you have to take the gauge cluster with you, you can swap anything you want in there, and just find a port for oil pressure, tach line, temperature, and everything else like voltage, etc... all just works with sensors you install on the engine.

Anyway, I only mention that because the 3.4 V6/60 is getting harder and harder to find. The 3400 and 3500 motors are cheap now, and there are good used ones still out there. So, something to think about.

BillS

FEB 22, 11:28 AM

I built a turbo engine (c. 300 bhp) back around 2000 that used a stroker 3.1 crank, (3.4s weren't easy to find parts for back then) a specially designed cam (Comp Cams) and fome good forged pistons and it held up just fine until I sold the car 20 years later. I limited boost to 10 psi and never had any issues. It was a lot of fun and very reliable.

[This message has been edited by BillS (edited 02-28-2025).]

Dennis LaGrua

FEB 27, 03:34 AM

quote

Originally posted by BillS:

I built a turbo engine (c. 300 bhp) back around 2000 that used a stroker 3.1 crank, (3.4s weren't easy to find parts for back then) a specially designed cam (Comp Cams) and fome good forged pistons and it held up just fine until I sold the car 20 years later. I limited boost to 20 psi and never had any issues. It was a lot of fun and very reliable.

I believe that forged pistons and the 3.1L does improve reliability. I know a few guys who rebuilt the 2.8L engines, with a cam and porting that ran high 14's in the 1/4 Mile. Thats not slow but it isn't very fast either. If you evaluate cost vs HP IMO,the engine swap makes the most sense. For this option, the engine was designed and built to make more power by GM from the ground up.