[riscy]

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.

 

[DougE]

There are so many wires associated with the stock computer that I just don't want to go down that rabbit hole. No telling what the PO has screwed with in the existing wiring system. On the S15 I'll be doing a Holley Sniper for its simplicity and ability to control 2 radiator fan circuits. On this S10 I can probably do a new carb for half what the Sniper would cost me. It seems common to adapt a Weber to these things so I'll probably investigate that a bit. I am looking for a detailed installation of a Weber so I can evaluate it.

 

[jimmykicker]

There are so many wires associated with the stock computer that I just don't want to go down that rabbit hole. No telling what the PO has screwed with in the existing wiring system. On the S15 I'll be doing a Holley Sniper for its simplicity and ability to control 2 radiator fan circuits. On this S10 I can probably do a new carb for half what the Sniper would cost me. It seems common to adapt a Weber to these things so I'll probably investigate that a bit. I am looking for a detailed installation of a Weber so I can evaluate it.

Do it like I did if you're concerned about it the wiring. My truck is a 1984 and was carbureted from the factory. I just took a 1991 ECM and harness, studied the diagram like I was studying how to defuse a bomb, clipped out the wires for power and then powered the system independently from the rest of the stuff that's basically the same from 1982 on. There's a fuse block I installed on the passenger side under the glove box that controls the EFI 100% so if I ever a problem, I know exactly where to look. When you look at it from the standpoint that this is in effect the way GM did it, it isn't so bad. The EFI harness has nothing to do with the other electrical system of the truck (regardless of year) other than getting power for it for the most part. Trust me when I say the most difficult part of wiring that truck is the part you're going into from the bulkhead.

PS. I kinda think it's badass you're putting one back stock that had a V8 conversion. Why? Well, I'm just like that I guess.

Carry on.

 

[riscy]

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!

 

[DougE]

This is what I find when I look for computer documentation. So much more complicated than a pre-computer system.

 

[DougE]

Just so you know guys, I really appreciate the input!

 

[riscy]

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!

 

[DougE]

Does anyone have a wiring diagram showing only the wiring necessary to make the engine run?

 

[riscy]

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

 

[DougE]

riscy, I appreciate your effort but dang, that's a bunch of wiring connections to run down without knowing what the ramifications to the computer would be.

 

[riscy]

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…

 

[DougE]

Well Darn!
Compression Test:
150...120......80....1,2,3
150...120...120....2,4,6
Squirted in some gear lube and #3 came up to 150#, So must need a ring job.
Suspect I can find a 3.4 in decent shape for less than the rebuild.

 

[riscy]

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!!

 

[DougE]

Trying to keep this reasonably low buck but not restrained by cost when justifiable. Obviously the 4.3's are later and easier to source. The odometer showed about 125k miles and the trans had been swapped. Not settled on a course of action yet. Just looking for low cost, but reliability. All the 2.8 stuff is supposed to fit the 3.4 block but don't quite understand how the 2.8 heads could work with the extra displacement and keep the same compression ratio.
Update: Went into RockAuto and checked cylinder heads of the 2.8 and 3.4. Hidden in the Info is both heads have the same interchange number:
OEM / Interchange Numbers: 3061272B
So must be identical!

 

[riscy]

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.

 

[DougE]

Bore and Stroke:
2.8L: 89mm x 76mm (3.5"x3.0")
3.4L: 92mm x 84mm (3.6"x3.3")

 

[ScottyV1966]

Like riscy is saying, the 60 degree V-6 has alot of variants that were in a ton of Vehicles. there are Plenty of Donors at your local Yards. I'm sure you could figure something out to make a reliable engine out of the V6.
Good Luck,
Scott

 

[DougE]

I'm just up the road from San Antonio, Texas. Must be someone down there that could help hook me up with a low mileage 3.4L.

 

[riscy]

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!

 

[DougE]

Texas goes by the 25 year rule also (yea!). If the engine comes with the harness I'll investigate using it (the multi-point fuel injection would be nice) but still, I'm concerned about what wires can be eliminated for an "engine only" configuration as I'll probably have to go with a basic hot rod gauge set. The best donor appears to be a '93 to '95 Camaro.