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Hello all! Figured I'd start a new thread to document the V6 engine swap, collect the various bits of information I've gathered from my own experience, and hopefully provide a bit of insight for others interested. Maybe Ed Mc can add this to his growing compilation package which he distributes to anyone who asks. Many thanks especially to Ed, geoffinbc, and Jerry Lemond for their gracious help (and anyone else who has helped along the way - didn't mean to intentionally slight or exclude anyone).

First, the vehicles:

1989 Trooper "Obi-Wan" - originally had a 2.8L V6, manual transmission, previous owner had done several upgrades to suspension/steering and added a 2" lift kit. Engine had a serious lower-end knock and evidence of having been wheeled through some fairly deep mud when I bought it. It would crank and drive enough to make it around the yard a few times, and maybe down to the mailbox and back. I knew it was going to basically require an engine swap, so I began searching. I had not done much with V6 Troopers up until late 2014, when I bought this one listed on Columbus, GA, craigslist. After searching for information on suitable replacement engines, I located a 3.1L with a blown head gasket from a 1990 Pontiac 6000 (transverse mounted - more discussion on this in a bit), which only had 131k miles and seemed to have been fairly well-treated, based on the condition of the donor vehicle.

Obi-Wan_towing_home.JPG


It just so happens that this engine already has the correct placement of the starter (driver's side), but it had aluminum heads, and smaller combustion chambers, so it came with "deep-dish" pistons to compensate. In order to bring the compression back up to where it needed to be for this engine to run well with cast-iron heads (larger combustion chambers) from the original 2.8L engine, I installed a set of 1992 Camaro 3.1L pistons.

Obi-Wan_shallow_pistons.JPG


NOTE: This is the 3.1L transverse-mounted, front-wheel-drive engine, NOT the 3100-series engine. The crankshaft main bearing cap bolts are different on the 3100 or 3400-series engines, and while these engines will work in a Trooper, the oil pan requires significant modification to get it to clear the front axle. Geoffinbc and Ed Mc., as well as others, have documented this information elsewhere (See this thread: Installing a 3400-series engine with oil pan). I asked my local machine shop about the possibility of retro-fitting the older two-bolt main bearing caps into the newer 3100- and 3400-series engine blocks, and they stated the main bearing caps and crank would have to be line-bored to work properly; not something they wanted to tackle. I suppose you could just use two bolts to hold the main bearing caps in place, but you'd still have to figure out the deep-sump, tin oil pan installation.

The 3.1L engine block has the correct three-bolt bosses for the engine mounts. Only thing I had to do was shim one of them with a washer to make certain the bracket bolted up properly. Forgot to get pictures of that, but might be able to get back under the hood and snap a picture or two.

It also would be a good time to document the availability of these engines:
1989 - 1991 Pontiac 6000/Sunbird
1989 - 1992 Pontiac Tempest/Grand Prix
1989 - 1992 Buick Regal
1989 - 1992 Oldsmobile Cutlass/Cutlass Supreme
1989 - 1992 Chevy Lumina and APV minivan/Corsica/Beretta/Celebrity
1989 - 1993 Chevy Cavalier

All of these vehicles are readily available here in the U.S. from just about any salvage yard. I normally pay anywhere from $125 to $250 for a complete engine with accessories, depending on where I can get one.

I installed the Comp Cams 252 camshaft with new springs and lifters (next time, I may order the roller cam kit instead), shallow-dish pistons, new bearings and freeze plugs throughout, new timing chain, harmonic balancer, larger-bored intake, 5.7L throttle body with 4.3L injectors, and larger intake pipe on the oil pump. Also deleted the smog pump, installed an exhaust manifold from an '85 Chevy S-10, and rerouted the pulley belt while I was at it (pics in another reply below). All of this, including the machine work on the heads and block, came in at a little over $1100 total.

Here's the almost-completed engine, ready for installation. Note the tool I made using the distributor-driven oil pump cap from the 3.1L distributor shaft gear.

Obi-Wan_complete_engine_distributor_tool.JPG


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Next, a coworker said he had seen this one on his way into work. Went to look at it and discovered it is a 1990 model with only 75k miles on the body, but most of the engine was sitting in pieces in the back cargo area. Interior was in great condition, so I'm now the owner of another non-running Trooper. This one is an auto tranny, unfortunately (yes, I can hear the groans across the interwebs), but the wife likes it, and wants it for her daily driver, so here we are.

Meet "Leia":

Leia_before.JPG


Here's a snapshot of the engine parts sitting in the cargo area before I bought it.

Leia_engine_parts.JPG


The story was that the previous owner had somehow managed to trash the engine and transmission towing a trailer over the years and took it to a local repair shop to swap in a remanufactured engine and eventually have the transmission rebuilt. The repair shop installed a Jasper engine with an Edelbrock intake and carburetor, rather than the original throttle body (at a cost of over $5500, mind you). The owner would just shift manually through the gear selector, since the carb'ed engine setup wouldn't have provisions to control the transmission control module. The shop never could get the engine to idle correctly, so the owner sold the vehicle to the repair shop, since he no longer wanted to dump any money into it. They proceeded to remove the engine and returned it back to Jasper. So, it has been sitting for nearly a year with no engine and a transmission that needs rebuilding, but still has almost $2500 worth of new parts installed.

My plan is to rebuild a 3.4L, which I picked up from a salvage yard today, based on the previous success with the 3.1L rebuild in Obi-Wan.
 

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Here's the before and after of the block boss which must be ground down for the power steering pump bracket to mount correctly on the 3.1L engine:

Obi-Wan_engine_grind_before.JPG


Here's the result:

Obi-Wan_engine_grind_after.JPG


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Here's the pulley configuration with smog delete and rerouted belt tensioner pulley before the belt is installed:

Obi-Wan_smog_delete_before.JPG


Here's the result with the belt installed:

Obi-Wan_smog_delete_belt_routing.JPG


Hope this helps! More to come...
 

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The 3.1 build looks good! That's a decent price for the rebuilt engine/parts. You must have a very reasonable local machine shop. Last time I took anything to my machine shop I just about had a heart attack, the prices had gone up so much!

The 75K Trooper looks very straight and unmolested, except of course for the abomination of mechanical work the shop did! I can't imagine why they would have scrapped the TBI setup, it's very reliable and isn't that difficult to troubleshoot. Ridiculous having to manually shift the auto trans. The $5500 bill is staggering, and more than I paid for my first '90 V6 Trooper way back in '98!!! :shock:

BTW when you're building that one, it might be a good idea to install an external trans cooler and then upgrade the tranny fluid to synthetic. It would give the trans at least some chance of holding up to the power of a 3.4.

I've bookmarked your build thread and will add links/info to my swap package when we're a bit further down the road. The built 3.1 and a 3.4 swaps will be good contrasts to each other, I'm thinkin'.

Have Fun!..........ed
 

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Thanks for the words of encouragement, Ed! I can use all the advice and helpful hints I can get. Here's what the final product looked like, just prior to throttle body and exhaust manifold installation:

Obi-Wan_engine_complete.JPG
 

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You don't need to run those 4.3L injectors. You would be better off with 2.8L injectors and grabbing and ECM from a 3 1L Rodeo. This way the fuel map should be pretty much spot on.

4.3L Injectors and 2.8L ECM will run very rich on a 3.1L because it is already rich enough on a 3.4L.

Build looks good. The truck will fly with a 3.1L compared to a 2.8L.
 

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If it's running rich, it must be only slightly, since I'm getting better than 18.5 MPG. On a related note, is there a way to reconnect the oxygen sensor wire without having to swap out the entire engine wiring harness? That particular wire is a coaxial design with an outer shield wrap surrounding an inner core conductor. Mine has touched an exhaust manifold or something hot, and the insulation has melted between the wires, causing a short. I've cut the wire to remove the melted part, but now there are only 12-14 inches remaining, and I'm wondering if it is feasible to simply splice on an extension to reach the O2 sensor (an additional 18-24 inches), or if I can extend just the center conductor, since the outer shielding is not actually connected anywhere down near the sensor - only the center conductor is.

Here's a photo of the engine to rebuild...

IMG_20160225_084915.jpg
 

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Too bad you couldn't find an S-10 wiring harness in the wrecking yard and just strip out the O2 sensor wiring. The green center wire goes to the ECM (should be terminal D7); the coaxial shield to engine ground if I recall correctly. The big mess of ground wires that terminate in one big crimped lug at the pssgr inner wheel well.

Pretty sure the outer wrap will shield the O2 sensor signal even if it's only grounded at one end.

It's surprising you're getting such good mpg with the sensor not in the loop, just think what it'll be when connected!

If you were to splice in a piece of the coax cable, make sure the outer wrap is spliced all the way through as well. As long as the majority of the sheath is there, with continuity all the way to the sensor connector, it should serve its original purpose. Maybe try overlapping the wrap then soldering if possible, otherwise I suppose you'd have to twist it together to get 2 ends that you could join at each splice.

News Flash: I just found something I didn't know existed; here's an O2 sensor wiring harness 24" extension for less than $13 on eBay:

http://www.ebay.com/itm/161399013780

Maybe that'd be enough so that you wouldn't have to splice a chunk of shielded cable in the line; all you'd have to do is make one splice. Note that the extension harness has no shield.

The junkyard version of this would be enough length of the O2-sensor-end harness to reach the splice area.

One last thought: install a connector at the damaged area, and use an extension harness as well, so you can unplug it farther up the line if you ever had to pull the engine out again.

HTH............ed
 

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The shielding is not a necessity. It helps to reduce noise but it will work fine without. If you want to extend the wire a short un shielded portion will be fine. I would solder and shrink tube a new section on the stock wire and install a new weather pack connector on the end.

Are you saying your running 4.3L injectors on your 2.8L?
 

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Geoff, yes, I'm running 4.3L injectors in my 3.1L, but I'm still running the ECM from the 2.8L.

Thanks to both of you for your responses regarding the O2 sensor.

Found quite a bit of carbon build up in the donor engine.

IMG_20160225_203339.jpg


Looks like the number 5&6 cylinders were normal and 1-4 were running slightly lean.

IMG_20160225_203902.jpg
 

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kg4miq said:
Geoff, yes, I'm running 4.3L injectors in my 3.1L, but I'm still running the ECM from the 2.8L. Thanks to both of you for your responses regarding the O2 sensor. Found quite a bit of carbon build up in the donor engine.
Man, is that nasty! Definitely a full-blown rebuild on that one. In contrast, the engine I got from LKQ in N. Ca back in 2002 was clean as a whistle inside. No gunk in the oil pan at all. But yours has seen many years and Mucho miles!

Do the cyl's have a big ridge? If so, it's probably gonna need an overbore.
 

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Discussion Starter · #11 ·
No, not much of a ridge, surprisingly, but I think the oil changes had not been very consistent.
 

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kg4miq said:
It also would be a good time to document the availability of these engines:
1989 - 1991 Pontiac 6000/Sunbird
1989 - 1992 Pontiac Tempest/Grand Prix
1989 - 1992 Buick Regal
1989 - 1992 Oldsmobile Cutlass/Cutlass Supreme
1989 - 1992 Chevy Lumina Car/Corsica/Beretta/Celebrity
1989 - 1993 Cavalier
A caveat on the use of these 3.1 FWD engines (other than what came in the GM FWD minivans, with TBI intake & iron heads), there are 2 configurations used with the same block casting # 10110519 (1991-1993).

One has 2 reinforcing webs cast into the intake valley (which reduce noise, vibration, harmonics - "NVH"), and these webs are not machined down. They fit an MFPI intake used in FWD cars.

The TBI intake won't fit unless these 2 rails have been machined down .453", which was done on those vehicles equipped with iron heads and TBI.

If you happened to end up with one of the high-web blocks, you couldn't use it with a TBI intake. The way to tell the difference on a FWD-MPFI car is to find the block casting number.

If the casting number is on the left side of the block it is a high-web block. If the casting number is on the front upper area of the block it is a low-web block.

I can't tell in your picture but it sure does look like a low-web block. I reckon you'd have found that out when you went to bolt down the intake, for sure!

Crazy thing I didn't know, is that the reason they used a TBI intake and iron heads in the FWD "MPV" style of minivans was they had engine compt height limitations, and the TBI intake sits lower on the engine. How 'bout that! Learn something new every day!

Last thought on this is that the 2.8 block used in '91 Troopers has the improvements as well, so would be a much stronger block to use for a 3.1 build. Besides already having an oil pump with a 3/4" pickup tube vice the older engines with 5/8" size.

I've attached some pics, one shows a 2.8 block with no reinforcing inner webs; the others show the 2 configurations of the 10110519-3.1 blocks.

Happy Rebuilding......ed
 

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Good point Ed. Either way your not goin to hurt any of the blocks with the power were making. If you have one of the high rib blocks you could grind it until the TBI intake cleared.
 

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Discussion Starter · #14 ·
Having made further progress toward getting this block cleaned up and prepped for overhaul, I noticed an odd thing after pulling the oil pan. I checked the crankshaft casting and discovered it was a 3.1L crankshaft. Hmmm. Did this crank get used in both 3.1L and 3.4L engines? (ANSWERED BELOW) I seem to recall reading somewhere that the cranks are the same, but the piston height is different between the two engines. Or have I stumbled on a rebuilt engine which has 3.4L intake and parts, but a 3.1L short block? Guess I could measure bore and stroke to be certain. It is definitely a cast-iron head engine, with shallow dish pistons, so my guess is that the crank is the same between the two.

What say you?

EDIT: Found it! 3.1L versus 3.4L crank discussion

Looks like the bore is the only difference between the two engines, which makes sense, so the crank can be used for both. You guys probably knew this already, and I probably should have searched the forum before I posted the question, but thanks for being patient.

EDIT #2: Whoa! This link has an excellent discussion with pictures for comparison between 2.8, 3.1, and 3.4L crankshafts, as well as rebuild tips. Crankshaft discussion on Fiero forums
 

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kg4miq said:
What say you? EDIT: Found it! 3.1L versus 3.4L crank discussion

Looks like the bore is the only difference between the two engines, which makes sense, so the crank can be used for both.
Yup! 3.1/3100/3.4/3400 cranks all have the same stroke. Crankshafts for distributorless engines have a reluctor ring with a number of "teeth" or slots built in to trigger a crank sensor. Any of these crankshafts could be used in our distributor application, since the crank will install in an older block with no interference by the reluctor ring. It doesn't affect engine balance, either.

Which means a 2.8 Trooper block is a perfect candidate for a "Stroker" build, since the bores are same as a 3.1. Just use the "stroker" crank and 3.1 pistons meant for an iron-head engine.

Geoff built one like that for his Trooper, and so did I, back in '05 to an '89 Troop I picked up dirt cheap with a Very tired 2.8. It ran really well, with a lot more torque than a 2.8. With an overbore it's more like "3.2" in displacement, close to a 3.4. A good option for a rebuild and since it's the original block, no drilling to relocate the starter. I built the Troop for my folks, and it was passed down to my nephew. Keeping it in the family!!

Note to the inevitable question of why couldn't we then bore out a 2.8/3.1 block to 3.4 specs; the 3.4 block was a redesign with thicker cylinder walls to account for the increased bore size. The 2.8/3/1 blocks' cylinder walls would be dangerously thin bored-out that far, and with casting shift it's possible to cut into the water passages.

Just a bit more enlightenment to add to what may rival "the worlds longest 3.4 swap thread" here at the Planet!
 

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Just to throw a wrench into things. If one wanted you could get a newer 3500 crank and have a competent machine shop offset grind the large rod journals down to the early 2" Size. This could net you an extra .250" stroke. But since you might need crank cleanup and the machining tolerances might require a bit less offset for full cleanup a .200 might be more reasonable. I have looked at crank clearance and it looks fine in the block. You may have to make a slight notch for rod bolts in the pan rail with a die grinder. I think you will be in for custom pistons though because you will want the pin as far up the piston as practical in order to keep the skirt in the cylinder. I wouldn't just use shorter rods on a stock piston.

If my current engine gets boring this will be my next adventure.
 

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It is amazing how close in color our two Troopers are. I put a 3.4 in mine not long ago after my rebuilt 3.1 failed me. Or I failed it when I put it together. My 3.4 was in good shape so I put it together without going inside. Runs great. And for the first time I have no oil leaks! I kept the 3.1 for the future. I think it needs a replacement crank, but everything else inside is like your 3.1. Pistons, cam, roller rockers, bored and all that stuff. I will enjoy keeping up on this.
 

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Discussion Starter · #18 ·
Stopped by a new-to-me junkyard today (closer to home) and located a 3.1L in a Lumina APV minivan, with about 200k on the odometer. Already has the correct heads, pistons, starter location, and TBI intake manifold, so a LOT less work scrounging for me. Think I'll pick it up in the next few weeks, in order to have a spare V6 around (already have six spare 4ZE1 engines). Also picked up some front brake calipers for Obi-Wan, as well as another engine stand to work on the 3.4L, since both my other stands have engines on them currently.

EDIT: hess, I was glad to see you had yours back up and running. I kept up with your swap, too!
 

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kg4miq said:
Stopped by a new-to-me junkyard today (closer to home) and located a 3.1L in a Lumina APV minivan, with about 200k on the odometer. Already has the correct heads, pistons, starter location, and TBI intake manifold, so a LOT less work scrounging for me. Think I'll pick it up in the next few weeks, in order to have a spare V6 around (already have six spare 4ZE1 engines).
You can never have enough spares! There's always another ZuZu on the Craigslist awaiting parts!

I have a Firebird 3.4 core motor (it had a spun rod bearing) and a good 3.1/3/4 crankshaft, plus a set of Z34 DOHC pistons on rods, waiting for rebuild time in the future. Using the Z34 pistons with iron heads gives around 9:5 compression ratio so, with all the other hp-adders, should make a pretty strong 3.4.

Plus a new set of 3.1 coated O.S. pistons and a 2.8 block awaits if I ever feel that bug again.

The only limiting factor is space to store 'em!! :twisted:
 

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I have been accused of being a hoarder and now I see I am just a beginner! I only have 2-4 bangers in the shed and a 2.8 and a 3.1. My biggest issue is there are no junkyards for 175 miles that are open on weekends. I did make a 500 mile trip one weekend to Utah to get some impossible parts. My Spacer can haul a lot of parts! As the sun is out today and it is nice I think I will start getting the hitch on and maybe the rear bumper. I feel the pain on working away from home for weeks, but at least you have a good job. There a alot that cannot say that. My hours have been cut from the normal 50 a week on squeezing out 40. While I like the home time, my bank account has seen a lot better days.
 
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