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Resurrecting a 2.8L?

2183 Views 56 Replies 8 Participants Last post by  PeteD
I'm in the process of rebuilding an '88 S15 (new 350 engine, new 700R4 trans). I bought a second S10 for miscellaneous parts that had no engine, trans or driveshaft. I think someone had dropped a big block into it at one time. The 2.8 I pulled out of my S15 wasn't running according to the owner. So, if I strip the 2.8 down to the long block, what it the simplest way I can get the engine back into service? Is there a carb that will fit the existing manifold? Will the distributor work or do I need to drop something else in? I'm good on old school 350's but know nothing about these little guys. (Thinking of giving this to a neighbor that needs basic transportation).
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As someone who just went through a 2.8 complete rebuild I do have some insights - or at least opinions.

The biggest question, for me, is what are you planning to put it into? If it is a TBI engine (I assume it is because you asked about a carb swap) and you are going back into a TBI/ECM controlled S10, then I would just do a stock rebuild and drop it in.

I researched this stuff a lot, but this is the first I’m hearing about a “drop-in” carb. These guys know a LOT more about this stuff than I do, but if it’s a TBI manifold there’s nothing I know of that will just bolt in (but i’m curious to know what will).

If you modify the engine much you will not be able to use the stock ECM and that is where things go sideways. At the very least you will need to get an aftermarket 700R4 TCC unit to lockup the torque converter. Air conditioning, cruise control, and other items may all be affected once you bypass the ECM.

I had to stalk an Edelbrock manifold on eBay as they are not made any more. You are going to pay in the $400 - $500 for a used unit. Also note that that intake is 2-piece and you will need to make sure you get the 4bbl riser and not the 2bbl (unless you just go with a 2bbl carb - the Holley 2300 is a good choice with that riser). You will also have to fabricate a TV mounting plate as none of the aftermarket ones worked for me. Watch your hood clearance, though.

Regarding the distributor, the stock unit is for EFI only, and no one makes a carb/HEI version except for maybe DUI. Their site looks like they might be able to make one but it’s not clear - you’d need to call them. And it will be expensive.

In the end I had to fabricate an adapter and go with a Holley Sniper on the Edelbrock intake. I found a NOS reman’ed crank from a 3.1 (bolts in with 3.1 pistons) and will up your compression a bit.

I got an updated cam from Schneider Cams. They are very helpful and knowledgeable about these engines. Comp makes roller tip rockers.

I spent a lot of money on my rebuild (not even counting the Sniper). As others have said, this thing pulls like crazy off the line, then gives up around 3200 RPM.

I do have one of the Edelbrock manifolds (used in good shape) and 2bbl risers (brand new) that I am about to sell. If you want to go the performance TBI route, I also have a TBI intake and throttle body that have been bored for more air flow (by me - not a machine shop) that would need new injectors - but going that route will lead you down a very difficult ECM path.

long post - sorry! But as I just got through this I have a lot to share. And I’m still fixing issues.

if you have any questions feel feee to reach out.
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This truck has none of the computer electronics. Is there a stand alone controller for the TBI? Gauge cluster is torn out so I need to go with old school gauges.
Hmmm… so it was a carbureted truck? Or TBI but the electronics are missing? Could you attach a photo of the intake? Or at least the years of the truck(s) and engine(s)!that are in the mix?

There is an ECU called Magasquirt that is very popular. diyautotune.com is a good place to start, and the pre-sales folks are very helpful. There is also Speeduino…. It’s open source, and cheap, but I could never get it to work.

going old school gauges with TBI will have a few challenges. If the truck was originally carb’ed then you’re probably fine. If you have pre-1989 TBI then you have a speedometer cable, but also a digital pickup in the instrument panel that sends the signal that the ECM needs. After 1988 the speedo feed is all digital. There are various converters out there that might get you the combo you need, but it’s tricky.
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I think he'd be fine on the AC and the cruise.
I agree if he runs a carb, but it sounded like maybe he wants to go with the TBI. And based on the ECM/ECU and what year truck he’s going into… I can see issues with VSS/cruise compatibility, and AC kick if non-carbureted, etc.

im just thinking about those “hurdles” you mentioned and the cost/complexity I went through - and still with unresolved issues, many of which are related directly to the 2.8 and its “uniqueness”…
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Per my initial post this is a 1988 S15 engine going into a 1988 S10 truck.
Thank you for clarifying - I wasn’t clear that the 2.8 was going into the “spare” S10. I also didn’t realize you were looking for quick/budget on the second build. Now I get it!!

My Chilton’s manual is for both the S10 and S15, and I haven’t seen them note any special instructions for the S15, so I think it’s safe to say that they are mechanically identical.

Do you know what engine originally came in the “spare” S10? That will have a huge impact on next steps…
Oh, and, regarding the A/C… this unit isn’t outrageous:

You’ll also need some parts:

Of course, all the tools can be “borrowed” from AutoZone (but their vacuum pumps are terrible, so find an A/C guy with a pro pump). I installed this in my 2.8l car and it was great. Assuming your evaporator & condenser are good you can do a full rebuild for under $500. All of my vacuum actuators were good and I was able to repair the selector switch in the dash, but you’re right - it can get expensive, if you can even find the parts…
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Wow - that S15’s gorgeous!!

For the S10…uh…

if you’re comfortable with all the wiring then the cheapest route would be to get a stock 1988 2.8 ECM with pigtail from eBay. You’d also have to get an instrument cluster with the cable-driven speedometer and VSS (here’s a terrible example:
1986-1988 CHEVY S10 SPEEDOMETER INSTRUMENT CLUSTER 25078792 | eBay). That assumes all of your sensors and accoutrements are working. (so maybe it’s not the cheapest).

The simplest route would be to put the Edelbrock intake and a carb on it as others have stated. I do have the Edelbrock base (used) and a 2 bbl riser (new) that I could sell for $400 (note that some carbs will mount “sideways” with the front of the carb facing the fender). You’d need to get a gasket for the riser and probably a carb adapter. And you’d need to get a stand-alone torque converter lockup kit and manual gauges. Cruise control is probably a goner without the stock speedometer with the VSS output.

If you have a carb that will work with the Edelbrock intake then the costs even out a bit. I’m sure I’m missing something, but that’s what I can think of at this point.
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Sounds good - let me know if you want to buy that carb intake. One other thing you’ll need for a carb is this:

Edelbrock 8179 Heater Hose Fitting 90 Degree 1/2 in. NPT And 5/8 in. Barb Clear Anodized Heater Hose Fitting https://a.co/d/7KfgUAO

The Edelbrock intake is based on the pre-TBI, and therefore pre-serpentine, 2.8. In order to clear the accessory brackets on your engine you’ll need that right-angle adapter for the heater hose. The Edelbrock fitting isn’t cheap, but I tried more affordable versions and they were all garbage.

The carb swap is pretty straightforward, except for the throttle/TV linkage. The Edelbrock intake I have came with some components for mounting, but I don’t think it’s a complete set. Just something to know if/when you decide to buy one.

let us know what direction you decide to go!
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This is what I find when I look for computer documentation. So much more complicated than a pre-computer system.
Yes, it is! But a lot of those wires aren’t truly necessary (EGR, AIR), or are redundant, etc. it’s not as bad as it looks.

They loomed all the ECU wiring into a larger engine bay harness that carries a bunch of unrelated wires. The PO may have left it alone since it’s such a pain to remove them. You might check under the passenger dash to see if the ECM wires/harness are still there and they just cut everything at the firewall… Heck, maybe the ECM itself is still under there :)

If it’s all gutted then it might make sense to talk to the guys at diyautotune.com about a MegaSquirt ECU with the existing TBI. They have a harness for it. Easier to wire, and probably cost about the same as a carb setup. You’d have to tune it, but they give support and MegaSquirt was basically designed to work with the stock GM TBI stuff.

If you do contact them they will ask you what the vehicle is going to be used for. You have to say “racing” or “off-road”, otherwise they will tell you they can’t help!
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That ECM diagram you attached earlier is basically it :)

you should definitely research/verify these, but this is the way I understand it…

A2 - A/C Relay Control: don’t know what this is for (A/C cut at full throttle?), but isn’t needed if deleting air conditioning
A4 - EVRV Control: not needed if deleting EGR. May result in Service Engine light being on all the time.
A5 - Service Engine: not needed if you don’t care about the diagnostic port
A8/A9 - Diag Input: same as A5
B2 - Fuel Pump In: could just tie to switched +12V if you don’t care about positive feedback
B7 - this is for the Electronic Spark Control module to tell the ECM to retard timing when knock is detected. Could ignore if you don’t have the module, or if you don’t care about knock. Could then remove knock sensor from block.
B8 - A/C Signal: I have no idea what this is for. Maybe disable A/C at full throttle? Can ignore if deleting A/C.
C2 - AIR Diverter: not needed if deleting AIR pump. May result in Service Engine light being on all the time.
C7 - High Gear Input: should only be for 4.3L

The rest are all needed, though it may be possible to just apply ground or power (don’t know which) to the Park/Neutral (B10) input rather than trying to wiring to the actual switch.

Let me know if I’m saying anything crazy :)
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I hear you! You were asking for the minimum to get the engine running… it’s my understanding that if you connected just the wires I didn’t mention you’d have a running engine. But, yah, it’s a long way to go for the remaining the wires and there’s always the chance that I’m wrong :)

And again, that’s assuming that all of your sensors work, etc.

Carbureted might be the way to go, then. You will still need a way to lock up the torque converter, though. There are threads out there that describe how that was done before TBI, and there are also aftermarket solutions…
Ouch - that does suck :/ Maybe the rings are just stuck, but yah, probably not worth the effort/risk.

Another thing to consider is a 4.3 with trans. You can get them cheap and parts are plentiful (many components are shared with standard small block Chevy V8). Good luck!!
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So, the 3.1 is a 2.8 with a longer stroke (different crank and pistons) using the same block and heads as the 2.8. The 3.4 is the same crank and heads as the 3.1, but a different block for larger pistons. Each progression (2.8->3.1->3.4) got much improved compression over the previous generation by using the same heads.
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Bore and Stroke:
2.8L: 89mm x 76mm (3.5"x3.0")
3.4L: 92mm x 84mm (3.6"x3.3")
so, the 3.1 would be 89mm x 84mm

there are a lot of 3.4 engines out there, but i’m not sure if any of the RWD versions were TBI. I think in the Camaro/Firebird they were maybe MFI at that point? Just saying be sure to get the ECU and harness from the donor vehicle.

Another thing to think about… I don’t know the rules in your state (TX?), but in GA cars over 25 years old don’t need emissions inspections. That means that you might be able to find a ‘95 or ‘96 3.4 with OBD-II, which would possibly let you tune it. I don’t know if they ever made a 3.4 RWD with OBD-II, but could be worth researching…

Let us know if you find anything!
Yah - the tuning aspect is what’s so difficult. The number of places able/willing to tune those OBD-I systems has dwindled. When you do find someone who can do it, I was repeatedly told they won’t “waste their time” on something that isn’t a V8/common engine. Doesn’t mean there isn’t a way to tune that stock ECM, it was just very difficult when I tried it.

That’s why I was bringing up the ‘95/‘96 (‘97?) engines - they would (possibly) be OBD-II AND out of the emissions requirements in most states - and tunable via software. Or get a MegaSquirt for the modded 2.8.
Yah, you can buy the proms and tuners, but it’s getting that “baseline” tune and being able to massage it that’s difficult these days.

SFI is intriguing. I had looked at a 3.4 intake and injector setup, but was too chicken to see if I could make one mate up to the 2.8. Again, though, you’d still be OBD-I and up a creek regarding a tune. You’d need to go with a…

O. M. G.

I just realized you could use a Holley Terminator X on a stock 3.4 intake on the 2.8 and have the best of all worlds. Even TC lockup control. Damn - wish I had thought that through sooner!!! 🤣
I don’t disagree. But the original premise what what could be done with a 2.8 and we’ve been riffing ever since :)
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