2.8 questions

[91_s_10]

hi, im new to this forum and have a few questions. I'm a big 88-98 chevy pickup guy and am really into the smallblock v8's. I recently bought a 91 s10 with a 2.8 and 5 speed tranny. The truck runs great other than leaking a little bit of oil, but what GM engine doesn't lol. long story short, what can i do to this 2.8 to squeeze a little more grunt out of it for passing power, hills and maybe some tire roasting once in a while, but still keep my great fuel mileage? I already put an injector pod spacer and throttle body spacer on the truck only to be disappointed. I'm not really willing to touch the bottom end or pull the motor but I'm completely open to doing a cam swap, intake work, and I'm probably going to mod the TB base to give it a little more air. Any suggestions on camshafts and lifters would be greatly appreciated.

[trotterlg]

There isn't much you can really do with it. Best thing would be to drop in a Camaro 3.4, but since you don't want to pull the engine that is out. The compression ratio on that engine isn't high enough to run any kind of cam that would do much for you and the iron heads flow very badly anyway. Larry

[91_s_10]

well i mean im open to tearing the heads off i just dont feel like going through the work of pulling the motor, if i have to pull it to work on the bottom end myself i will, but I don't want to spend the money for any kind of machine work, it's only my daily driver and i'd like to keep the cost as low as possible. Basically I want a little more power but keeping my reliability.

[trotterlg]

There is just not much you can easily do to that engine, the iron heads are just plain awful. Best plan would be to take a little ime and build up another engine, if you need easy use a 3.4 from a Camero. Sorry, there is no easy solution to power from a 2.8. Larry

[caffeine]

Probably a MPFI conversion should net better fuel economy and marginally more power but I wouldn't bother unless you're willing to learn how to tune a GM ECM. If you do that, you can also enable lean cruising and other fuel saving things to further increase fuel economy.

Other things like headers and cat delete IMO are good for both power and fuel economy; basically you're freeing up restrictions and the engine is already making the power, so you're improving efficiency.

An electric fan vs. a clutch fan will also free up some power though I don't know whether or not it would be noticeable. You can also use a FWD 3100/3400 water pump pulley to underdrive the water pump a bit for pretty much no cost and in my experience cooling won't suffer either.

I recommend the OBX headers that are sold on eBay for the S10 2.8. See the 3.1 SC Sonoma thread on this forum to see fitment etc... Stainless, very reasonably priced, and y-pipe fits well with a basic mod (cut out a section and weld in a flex pipe). They sound good too.

If you're seriously interested in a MPFI conversion I could help you out with the details. It will require some basic wiring.

[91_s_10]

Well i really didn't wanna play around with electronics or try and learn how to tune it on my daily. I thought about a v8 swap on this truck quite a bit since a have a 305 thats basically way too underpowered for anything else just laying around collecting dust. I think this truck needs the top end freshened up being that it has 160xxx miles on it. I think i might just try and swap in a bit better cam instead of doing an OEM replacement and just all new parts in the valve train. I'm not going for a powerhouse just a little more get up and go, by no means do i expect to build a wild 2.8 lol. I still have to do some thinking but i might just end up dropping in my 305. I'm just trying to plan out stuff before i go tearing into it.

[91_s_10]

but thank you for the info i honestly thought people built 2.8's for the f bodys and j body cars all the time

[robertisaar]

depending on how far you want to dig into it, you could make quite a potent n/a 2.8 using a gen3 topend.

[Guest]

but thank you for the info i honestly thought people built 2.8's for the f bodys and j body cars all the time

People do, but those are two very different engines, well, generations.

The problem is that small changes on the anemic genI 660 don't seem to make much of a difference, I mean bolt ons like you have found to be less than impressive. Headers will help, but only so much. The way to power is more air in and more air out, so the bottle neck being the heads is where one needs to look at to get some power.

There is the hybrid swap that uses a genII top end, but usually also requires swapping pistons as well, to keep the SCR in check. IIRC the genIII top end on an S-series 2.8L bottom end ends up around 12.5:1, which is a bit much for most pump gas applications, even though the gen III heads do have a good chamber design. This swap also requires swapping to MPFI with a different ECM, to keep things easy, since DIS is a requirement, which means that a crank trigger is also needed.
This is where most people start with a 3.4 as found in the '93 to '94 F-body, since it has the crank trigger already.

There is the option of adding a turbo, but again, for ease of tuning an MPFI swap is usually also accompanied with the turbo addition.

You may be happy with a cam swap, I know I wouldn't be. I'm HP hungry and love to get more power.

To be honest, your best bet is to learn how to tune through the ECM, it can unlock some power there and improve economy. There is also the fact that as you start changing things on the engine to get it to breath better, the tune in the ECM as it was originally programmed will now not be proper, leaving both power and economy on the table.

The 660s most commonly found in the J-body are of the Gen II variety, that came with better flowing aluminum heads, though not as good as genIII heads. Many J-body owners swap to the genIII top end to really open up potential, still others swap in the entire genIII engine for even more potential.