HI'S AND LOWS OF GM 2.8, 3.1, 3.4, 3.5, & 3.8 LITER ENGINES?

[CARNIGG]

Any body out there know much about the performance levels and potentials of these engines? I once had hold of a 89 cutlass with a 3.1 and minor mods and it was nuthin to be taken lightly. Anyway, just wanted to know the differences on these engines and ish like that...thanks..

[CARNIGG]

upp

[MagicRat]

Jeez, people have written books on this subject.

The 2.8 L was very reliable, especially in the iron cyl head version. They run forever, but had low power for their displacement, 110 to 135 hp depending on the year. This low power was just because they used a wedge style OHV cyl head, like on any old V8. This limited the breathing and rev range of the engine.
All this was fixed on the 3.4 L DOHC varient from about 10 years ago. Those engines were really good, but were expensive to make for otherwise humdrum cars so GM stopped making them.

The 2.8 got larger bearings in mid 1985. Earlier versions tended to spin rod bearings if overrevved. These engines reached theur best development in the Fiero. You can get 150 - 160 hp easily with bolt on manifolds and a camshaft. Serios headwork will get you 180. Use Fiero or Firebird /Camaro heads as they had bigger valves.

The 3.1 was a varient with aluminum heads. Those heads had canted valves and would breathe much better, but only raised output to 125 hp stock. Still there is more potential in a 3.1 than in any 2.8.

The 3.8 is a completely different engine design with huge potential. as awesome turbo variants were built for many different cars (ie Buick Grand National), and the supercharged versions are pretty quick too.
If you have a choice in a project, start with a 3.8. Its MUCH better than a 2.8 - 3.1

[CARNIGG]

I See Oldsmobile Cutlass Supremes With The 3.4 Engine...are Those Any Good?

[Evangelion]

Well now your looking at dohc vs single cam (regular)... both engines have extremely close HP most likely 3 -5 hp with in each other, i know the 3.8l out of a 98 is 200hp and i think the 3.4 is 195 or 198 something like that.

3.4 dohc - with some head work i suppose you could look at some nicer dyno records but you gotta put into perspective that means 4 cams..and a BELT ... you could custom turbo it, good luck finding a supercharger that bolts in with little to no problems.. as you can see im not a personal fan of the 3.4 but its still a nice engine and untill GM pep'd up the 3.8 it was the best managable v6.

3.8 - Stock, this engine comes with one major flaw, at 90k miles the extreme heat from the EGR dumping into the lower intake manifold that has a valve that dumps into the upper (plastic) intake manifold melts into a water jacket sitting a mer 2mm from the hole, thus causing small amounts of water to be sucked into your engine over the coarse of 3 days untill on day it doesn't get compression.... (yes this was a personal direct experiance with a 98 3.8 liter *sigh*) ..... however you slap a supercharger that comes with the supercharged Grand Prix you take care of that little problem, get some different pullies and some head mods from SLPerformance.com and you can probly push 300 to the ground.

As for the GM 4-bangers... i am very unimpressed... you can do some major engine and intake (turbo) mods and maybe get something kinda fast.. but i wouldn't mess with them personally.

[quaddriver]

Originally Posted by MagicRat

Jeez, people have written books on this subject.

The 2.8 L was very reliable, especially in the iron cyl head version. They run forever, but had low power for their displacement, 110 to 135 hp depending on the year. This low power was just because they used a wedge style OHV cyl head, like on any old V8. This limited the breathing and rev range of the engine.
All this was fixed on the 3.4 L DOHC varient from about 10 years ago. Those engines were really good, but were expensive to make for otherwise humdrum cars so GM stopped making them.

The 2.8 got larger bearings in mid 1985. Earlier versions tended to spin rod bearings if overrevved. These engines reached theur best development in the Fiero. You can get 150 - 160 hp easily with bolt on manifolds and a camshaft. Serios headwork will get you 180. Use Fiero or Firebird /Camaro heads as they had bigger valves.

The 3.1 was a varient with aluminum heads. Those heads had canted valves and would breathe much better, but only raised output to 125 hp stock. Still there is more potential in a 3.1 than in any 2.8.

The 3.8 is a completely different engine design with huge potential. as awesome turbo variants were built for many different cars (ie Buick Grand National), and the supercharged versions are pretty quick too.
If you have a choice in a project, start with a 3.8. Its MUCH better than a 2.8 - 3.1

the gen1 660's were hideously unreliable and had MAJOR oiling problems. power ranged from 110hp to 135hp in the HO version

the 2.8 block underwent changes thru the years to improve oiling and the heads/intake. gen2 came out with splayed valve aluminum heads and flow pretty good but still have crappy intakes - all overcomable - 250hp from off the shelf gm parts is a daily reality. 3.1 was a stroked 2.8 and hp was for the most part 140hp advertised and a 205hp turbo version. gen2 2.8s made 125ish in either MFI trim for J/L/N cars and 125 for TBI version in S/T

the 3.4DOHC variant was an abortion based on the gen2 that should have never been built. yes, it made 205-215hp but had zero gasket reliability, is a servicing nightmare and has impossible to get at accessories.

the 3.4 is a bored version of the 3.1 and exists in gen1,2 and 3 trim...gen1 for a 2.8l drop in for old s10s, gen2 was used in the dustbuster and gen3 is used in the L/N, B, W bodies today.

actually the 3.1, 3.4 and 3.5 all exist as gen3s and still have different gasket problems and knock problems, but finally oil pretty well.

the 3.8 you are referring to is likely the buick version, the chevy version didnt survive much past the early 80s (and was avail as 3.2 and 3.8 displacements) the buick had 3.0, 3.3 and 3.8 of which I think only the latter still exists, the 3.3 was a mainstay of the GM A body until recently...it is a completely different animal and far more refined and utterly bulletproof. hp ranges in the 3.8 from 165 up to 240 depending on trim, and 300hp at milford. the 3.3 actually had only 5 hp less than the majority of 3.8s produced, but had a lot less torque and no balance shaft.

[CARNIGG]

Question?......How can GM get away with the making of one engine (3.8) for so many years and have it be highly successful? That block or should i say that displacement has been around for years. I mean, was it that good a design from birth or what? And I guess no matter how good a cutlass with the leather and a 3.4 DOHC badge on the side looks, is it just safer to stick with the 3.1?

[daveo211]

Originally Posted by Evangelion

Well now your looking at dohc vs single cam (regular)... both engines have extremely close HP most likely 3 -5 hp with in each other, i know the 3.8l out of a 98 is 200hp and i think the 3.4 is 195 or 198 something like that.

3.4 dohc - with some head work i suppose you could look at some nicer dyno records but you gotta put into perspective that means 4 cams..and a BELT ... you could custom turbo it, good luck finding a supercharger that bolts in with little to no problems.. as you can see im not a personal fan of the 3.4 but its still a nice engine and untill GM pep'd up the 3.8 it was the best managable v6.

3.8 - Stock, this engine comes with one major flaw, at 90k miles the extreme heat from the EGR dumping into the lower intake manifold that has a valve that dumps into the upper (plastic) intake manifold melts into a water jacket sitting a mer 2mm from the hole, thus causing small amounts of water to be sucked into your engine over the coarse of 3 days untill on day it doesn't get compression.... (yes this was a personal direct experiance with a 98 3.8 liter *sigh*) ..... however you slap a supercharger that comes with the supercharged Grand Prix you take care of that little problem, get some different pullies and some head mods from SLPerformance.com and you can probly push 300 to the ground.

As for the GM 4-bangers... i am very unimpressed... you can do some major engine and intake (turbo) mods and maybe get something kinda fast.. but i wouldn't mess with them personally.

I must disagree with your notion that the GM 3.8L v6 has a "major flaw" I've been around the 3.8L(front drive i assume since you mention a plastic intake cover) for some time now, and the only "problem" the engine has is that it outlasts the car's body. I've got 156,000 miles on a 1999 lumina in my driveway that has had absolutely no problems ever. Like with any auto though, it has to be well maintained, and correctly maintained. did you change your antifreze shortly before this happened?? there is a special fill procedure for this engine so as not to trap a bubble of air in the intake manifold coolant passage. Also there are any number of intake plastic cover arrangements, they are not all the same, and it's possible that we don't have the same one. My egr isn't clost to ANY plastic at all. I've heard NUMEROUS reports of this happening with the 3.1 frontdrive v-6. those I wouldn't touch. I've found the 3.8 to be nothing short of bullet proof, and have heard of no problems that plague it.