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1991 Isuzu Trooper LS - resto 3.4 swap

13K views 42 replies 9 participants last post by  lorenzo816 
#1 ·
So I got wind of an LS up the road from me about an hour away for sale for a great price.
Turns out the motor sounds terrible and the 4L30 needs some love. The interior was in great shape and the truck overall wasn't abused.
My plan was to find another 2.8 and an mua5 or a 3.4 and an mua5 and drive it for a bit and sell it.

Here are a few pics of when I got it.
She looks great actually. All electric windows, seats look great, interior carpet could use a scrub, but over all just some age and minor surface rust here and there.
And it came with 5 snowflakes and four 'asterisk' wheels too!



A few days after I picked up the black one, through some Zu fam grapevine, I heard of another 2.8 '91 LS with an Mua5 for sale for a great price.
Bad thing is that it was almost flipped and the top was cut half off of it. But at least the drivetrain was there!
Mileage was super low and the guy showed me a video of it running before I decided to drive out.
Since this truck was on the Eastern side of NC, I decided to make a trip to OBX out of it and took the fam on an excursion.
The guy was super nice and let me load the truck and leave it there until my return trip from the beach. Super awesome.
This is Larry the guy who sold me the 'half' trooper. He was happy to see his beloved Trooper live on in another Zu and stay within the Zu fam.


So here they are when I finally got them home and unloaded.


I don't know yet how far I am going to take this Resto.
I'm going to sell everything I don't use, so if you need something, go ahead an PM me.
I plan to service the 4L30 completely minus a band replacement job and sell it. I'm sure someone needs a 4L30.
For the 2.8 that feels thrashed, I dunno yet what to salvage off of it but will find out soon.

As for the running half-trooper, I need to get gas to the engine. The video I saw and I also did this in person was puring gas down the TBI and it sounded great actually.
Problem is its not getting fuel from the pump. So last night, I cut a hole in the rear floor to pull the pump out and replace it.
I'm going to put a new filter inline before I fire it up of course.
I want to get the half-trooper running good before I pull it out.

I'll post pics as I go. Any advice, opinions, or criticism from the Zu fam is welcomed.
I may need some 2.8 spec data as I go.
 
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#2 ·
Looks like a double score to me. Fortunately, with BOTH Troopers, you have everything needed to do the auto-manual swap. Personally, if I had mine to do over, I would have just rebuilt the 4L30E, but that's all hindsight now.
Definitely want to follow progress on this project, so keep posting. Dennis
 
#3 ·
Thanks Dennis.
So the fun finally begins.
I'm going to nickname the donor truck "choppy" to keep things straight when I'm talking about which LS I'm working on.
Anyhow, so I wanted to get Choppy to run on its own power before I started ripping it apart. Little sanity check ya know.

I cut the hole in the rear floor of Choppy so I could pull the fuel pump out. I never heard it hum when I turned the key so I figure it was the culprit.
I've struggled with the fuel pump phillips heads before and I knew better than just go at it and break them off in the process.
I didn't have any PB blaster so brake fluid will have to do.
A weekend later of soaking and I did the head bolt tap trick. Smack the driver with a brass hammer and then turn. Voila all of them came out. Oh but that smell. Barf.
Yep rusty as all get out. I mean baaad. Smelled like turpentine bad.



I wish all these damn trucks had gas drain holes. Anyhow
So I drained it, I put a little fresh gas in and put in an older Rodeo fuel pump in and went to the store to get a battery.
Both extra batteries I have were just not cranking at all even after charging. Sucks to have to cough up another $150 but oh well.
After a few dry key cycles to get the oil turning over, she runs!! And she won't stay running but I don't care. The motor sounds great.
Ignore the busted exhaust but she runs. Video here: https://photos.app.goo.gl/1U2PfsbeZ3YmfNjN7


Now the next part of the project is to pull the motor and trans out of Choppy and salvage what I can sell and save what i need for the Black LS.
Following tearing down and parting out what is left of choppy, will be servicing the 4L30 from the black one and selling it off. Any takers?
:wink:
 
#4 ·
I bet you were happy to hear it run! And only 125K on the donor vehicle, low miles!

BTW don't scrap the noisy 2.8 in your Black LS, at some future time you could tear it down for a rebuild and do the "3.2 Stroker Mod" to it. With a good cam, maybe some 1.6:1 roller-tipped rockers and a Big-Bore Intake/TBI, it'll have plenty of pep and run rings around a stocker 2.8.

But at least you've got what sounds like a decent engine to work with for the black LS, to get her going again. And quite a treasure-trove of parts on "Choppy".

Sure does save on trips to the wrecking yard, it's only a few feet away! Really nice having every piece imaginable to do an auto-to-manual swap.

Cheers..........ed
 
#5 ·
Slow progress. I been busy as snot lately but that is usual the norm for me.
I started pulling everything off I can from Choppy and putting parts in my shed.
Listing a bunch of stuff here for sale too and on FB isuzu trader.

Here Choppy sits until I can find another day to work on the dismantling.


Making a mental list of upgrades so far for the Black LS:
  • revo gears[/*]
  • poly bushings + lift shackles[/*]
  • poly sway bar bushings[/*]
  • heavy duty tie rods[/*]
  • hoping to get some steel braided brake lines too[/*]
  • I may bypass the clutch damper too[/*]

Anyone have any gotcha's I need to keep in mind for the 5 speed swap?
  • pedal assembly[/*]
  • computer[/*]
  • slave + master cylinders[/*]
  • driveshafts[/*]
  • is the exhaust any different?[/*]
  • cross member for trans[/*]
  • shift boots and console area[/*]
  • anything else I'm forgetting??[/*]

Looking forward to a weekend in the woods here soon.
I'll pick Jerry's brain and Pauls' while we're there.
:bigsmurf:
 
#6 ·
Get back to work!
 
#7 ·
Which work?! :D

So this past weekend got some time on choppy after helping Nate with his carrier on the split driveshaft.
We got soooo close to pulling the engine out before it got dark. I need to get a few more bell housing bolts out drop the trans.
I should've just got the front 10 bolt out the way too. Might've made getting to those exhaust studs easier too.
Anyhow, weekends are getting scarce where I can just work on it. Once I have choppy out the way, its onto the Black one!
Sorry no cool pics yet!
 
#9 ·
Sitting for now. I'm parting out this other LS first and need to get the engine out of both of them before I dig into the black LS.
So slow start but should snowball once I get going.
 
#10 · (Edited by Moderator)
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Got the engine and the transmission out this past weekend of the donor.
Saving the exhaust pieces and crossmember, driveshafts & pedal assembly for the black one!
I forgot to detach the accelerator cable and got hung up for a minute. Couldn't figure out why. Damn obvious. :roll:

Once I get everything out of choppy I'm gonna have to take a break and move onto my Audi.
Only have weekends and plus getting dark at five doesn't help.

Don't know if you guys saw but did you see the bring a trailer auction for a red LS that went for 10 grand today?
 

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#11 · (Edited by Moderator)
Small update.
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Through the Zu fam network I scored some nos boots!!
Haven't pulled the truck up yet to start digging in but will after I work on my Audi.
 

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#12 ·
I owe everyone a long update.
Its kinda funny actually. I'll cut to the punchline.
I bought another truck. :lol:
I found a bronze/white 88 4 cylinder stick shift about 40 mins from me. Long story short, I was picking up a shop press and saw the trooper around back. I asked whose was it and then struck up a conversation with the old man owner of the truck. He liked the fact that I was into Isuzu and agreed to sell it to me. By the time I got around to going to get it, the thing blew a head gasket. So I offered him a bit less and drug it home.
Now for the fun part. I now have all kinds of experience on these 4ze1 motors. I helped Nate swap his head now twice. The rockers keep breaking! Different story for another thread. But when it came time to doing my head job, two of the spark plugs got stuck and broke off inside. Oh I just about cried and had to pull the head back off. I know I know. I should have done the previous plugs on the bench. Anyhow. that 88 is just about 2 hours away from being done. Just needs the front belts, ps pump, alt and radiator put back on.

I also got a 3.4 in the past few months!.
More on that in a bit....
 
#13 · (Edited by Moderator)
okay so here is a rear pic of the 88 bronze trooper after I got snowflakes and new rubber for it. Damn thing actually has a better frame than the black LS. I'd swap it if I weren't already over my head in projects!
I plan to clean up the other 5 snowflakes and then swap the new General Tire rubber to those for the Black LS.
Yea I know, I know pay labor to swap tires but I wanted the bronze one to have better meats than the stock asterisk wheels and pizza cutter rubber.
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I'm not sure if that photo is sideways just for me or everyone else.... hmnnn

So back to the Black LS!
I started pulling everything off the bottom so I could pull the trans out and then yank the engine.
I cut the exhaust where the bolts wouldn't come free. And out comes the heavy sob 4l30e. After talking to Garret, he's going to help me freshen this up with confidence so someone else can take it off my hands.
If you don't know Garret, he is Marcus in MD's son and is a whiz at working on those 4l30's.
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If you notice in the pic above, I actually have one of those coveted skid plates. Well I between the two trucks have a complete set! Plus the long one that goes from the front skid to the front crossmember.
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#14 · (Edited by Moderator)
So in the spring, I found a guy up the road who all he does is mess with Camaros. I told him I was serious about the 3.4 and he let me go do a compression test on it.
Everything was within 150-160 so good enough for me. If I decide to do rings later on, I can while the engine is out but for now the plan is to just go after some regular upgrades and drive the beast.
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And maybe I'm the crazy one here but why not just keep the MPFI? I have the computer and wiring all of it.
I managed to find some FSMs online for that era Camaro/Firebird and am going to see what I need to do to map the pinouts where needed to just keep the MPFI.
If anyone has done this, I'd like to hear about it. I don't think this should be that hard and I don't like the idea of going to TBI and a 3.1 computer to run the 3.4.
Seems I have everything here to get this done as-is.
I'm all ears though.

So now I have 3 engines sitting in my shed and I need to finish up that 88 and in the middle of all this awesome sauze, the wife has me doing wood floors in the house.
And I had a hair brained idea to get the frame out as a roller and get it blasted. :shock: :lol: :shock: :lol: No bu\\sh*t.
THIS PROJECT IS NEVER GOING TO GET DONE! :bom:

...in the meantime, I'm keeping my eyes out for cool stuff that would really make the black LS complete.
I got a stock grey cargo cover from a guy about 2 hours east and Ian helped me get this stock bull bar from a guy in KY.

No I'm not kidding on the frame blasting though. I really want this to be super nice. After seeing how nice the 88 bronze/white one was, I couldn't just spray can the frame on the Black LS.
I just can't leave it alone like that. Anyhow, I need to get to tearing down that 3.4 and beefing it up. I have a lot of learning to do on that motor but I bet its simple stuff since 60 degree stuff was so super common back then. I need to read more but hoping to find some cams for it, headers... what not.
IMG_5710.jpg


Anyhow, I'll keep posting as i hoard parts or get progress done.
For now the Black LS sits a shell. It can roll but has not guts. :bigsmurf:

 

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#15 ·
YOu can always count on the wife to pile on more projects when you are drowning! :lol: Wood floors.....oof been there done that. Please tell me they are not unfinished.

BTW which dude in the pic is you and which is the guy getting out of the zu bidness?

I'll be in the peanut gallery.......carry on
 
#16 · (Edited by Moderator)
This is me after I busted my window out last weekend.
Damn tree jumped out at me.

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Shows up sideways again for me.... Hope it is straight for you guys.

 

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#17 ·
If you're into doing that kind of wiring, yes it is indeed possible. One of our members retained the SFI system. I'd expect you might get a smoother output, better mpg and perhaps a cleaner torque curve with the more-sophisticated SFI system. But you'll be limited to around 160hp if you keep it stock.

The TBI system is maybe a bit cruder, but with a bored intake and throttle body from a 4.3 GM V6, it flows lots of air. With 1.6:1 roller-tipped rocker arms, Holley Big-Bore TBI atop a bored-out intake, 2-1/2" free-flowing exhaust, I'd estimate at least 180 hp. An S10 Dude that had pretty much all those mods, and IIRC a performance cam, plus headers, dyno'd his S10 at 187 RWHP. That's over 200hp at the flywheel.

I'm still running the stock 2.8 ECU after 19 years, and with a new battery that isn't dragging the system down, the engine runs better than it has in a long time. I do have a 3.1 ECM I've been meaning to throw in there, but it runs so good I'm not bothering to do so at this time.

The main reason folks are leaving it as a TBI setup is simplicity; with only a few "kinks" the 3.4 swap is nothing more than an R&R. But if you're up to it, By.All.Means.

Note that if you jack the fuel pressure up via modifications to the fuel pressure regulator or stiffer F.P.R. spring (the yellow 14 psi spring), you can even run the old 2.8 TBI. The top-end will be limited, as the 2.8 TBI doesn't flow enough air to feed the larger engine properly. Good low-end torque, though.

Do a writeup for the rest of the ZuZu folks when you're done.

BTW 150-160 psi should be Good to Go. I would still pull the intake manifold and check the lifters for auto-rotation as you're turning over the crankshaft. It's not unheard of on these to have a flat cam lobe or 3. If even one lifter doesn't rotate as you turn the crank, the cam is Junk.

Re-seal the intake with a quality RTV such as the GM-spec stuff or Permatex Ultra-Grey (which I expect is very similar to the GM RTV). You don't want any future coolant leaks there.

When you're installing new intake gaskets, DO NOT cut the gaskets to get them around the pushrods. Use a Lisle pushrod tool https://www.ebay.com/sch/i.html?_from=R ... 00&_sop=15 and you can pull the pushrods without affecting valve lash. A great option if you don't otherwise have to disturb the valvetrain.

Also replace the timing gear set and the timing damper that rides inside the chain and gears. Definite wear items that'll bite you later if you don't.

Use the larger-diameter clutch meant for a '91 3.1 Pickup, if you order one for the PU it'll Guarantee Fit. Handles the extra power a lot better. Resurface the 2.8 flywheel or replace it, so you'll have a smooth surface for the larger disc to ride upon.

Have fun with all the projects, I'm up to my Ears in yard wall/driveway projects and Mustang Stuff. At least the Trooper's running great!

Cheers..........ed
 
#18 ·
Ed I appreciate your wisdom and thoughts on the swap.
Are you saying keeping the mpfi is going to lock me in at a top-end HP range?
Well then boohoo, I guess I'm going to use that dang TBI after all. I'd love to open the hood though and see a much smoother intake setup. But if I can't get the 'look' for the HP, then so be it.

Maybe I need to do some more googling on tweaking that 3.4 with the mpfi to see the upgrade options vs. the TBI route.

As for the maintenance items, for sure! Darn right we're going to replace all the little pita peices that bite you later on. Even if it is going to nickel and dime me to death.
 
#19 ·
Not saying you couldn't get more power out of an SFI iron-head engine, but there doesn't appear to be a lot of market support for that. Probably because the more performance-oriented folks who are running F-body Camaros and Firebirds get the V8. And the short amount of time this unique engine was used ('93-'97).

I saw an engine build for a Fiero where they bored out the 2.8 Fiero throttle body and port-matched the 2.8 MPFI intake manifold to the heads. You might gain a bit there, and maybe there's a larger throttle body available for the SFI setup. Dunno if you'd need to upgrade to larger-size injectors. They used an FWD block with roller-cam setup, but other than that the techniques and parts they used are indicative of what you need to do to wring more power of of the 60-degree RWD block.

https://web.archive.org/web/20180620063 ... etails.htm

IDK if the SFI manifold makes more power than the 2.8 Fiero MPFI, which is rather unique in itself. It probably wouldn't be any easier to wire in the MPFI system vice SFI, but there would be a lot more support for Fiero stuff. Try Rodney Dickman Fieros for that. They're the website selling the starter drilling jig, since the Fiero Dudes do a lot of 3.4 swaps into their rigs.

And of course you could throw a Comp Cams kit in it. Depending on what you're looking for (either lots of low-end torque for trailing, towing, etc, or mid-to-hi-range power for highway work), you could use their "252" kit (torque) or the "260" kit, which is "hotter".

Either cam kit requires higher-grade valve springs (the Comp Cams full kit comes with everything you need), and you'll either have to do that replacement with the heads in place (using an air fitting to pressurize the cylinder and keep the valves from falling, or the old-time trick of bringing the piston to TDC and filling the top with some twine/rope thru the spark plug hole), or pull the heads. At that point, might as well have them gone thru!

And of course when you've finished that task, you'll have to set up the lifter pre-load and break-in the cam.

So that's totally up to you, your skill and ambition level, and budget.

A bored-out 2.8 intake plus Holley Big Bore TBI (like the one I have on my '90 3.4 LS) or a GM 4.3 V6 TBI flows around 400CFM, which is plenty for the 3.4 unless you're going "full race". IDK what a stock SFI throttle body and intake flow.

Perhaps you can find more info at this site, they have tons of info and discussions about all the variants of the GM 60-Degree V6:

http://60degreev6.com/vb5/discussions

Here's a search for "3.4 SFI" that pulled up lots of threads including some from "Canyonero" who is the other SFI-in-a-Trooper swapper. So you might take note of those. Same user name here, as I recall.

http://www.60degreev6.com/vb5/search?se ... 7zRdno23jw

It'll make you do a "CAPTCHA" before letting you complete the search. What fun! :evil:

Hope that helps!............ed
 
#20 ·
Ed, that Fiero build is inspiring. I'll do some digging but yes there is nothing off the table. From replacing the heads to using roller rockers and custom rods, I don't care. I want to squeeze as much power out of the 3.4 as I can get.
This isn't going to be a budget build, well, except for the parts I already have. :D
 
#21 ·
Another update.
And no I didn't buy another truck :D but yes there is another trooper at the house.
Not mine though. There was a fella up the road from me that wants the 2.8 I got from Choppy to replace his 2.8.
I tested his first and had no compression on two cylinders so at least Choppy's heart now has a home.
I'm half way done with the swap and good thing too, I'll treat this as a practice run on the black LS.
Automotive parking light Tire Wheel Land vehicle Vehicle

Someone used stop-leak in the white trooper so I took both my black LS radiator and his to a radiator guy to get cleaned out and repaired.
Both are original copper rads, not the slightly thinner new plastic aluminum rads that you get aftermarket.

I did also find a 3.1 computer! @Ed Mc. didn't you say that I needed the 3.1 ? Hope those numbers match and are legit!
One more question Ed. How many teeth and how large is the 3.1 flywheel? I remember you saying to run the 3.1 or can I run the 3.4 flywheel?
Rockauto is showing the same flywheels for the 2.8 as the 3.1 so I'm stumped here.
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@geoffinbc I sent you a msg on getting the intake bored out. Do you need just the upper intake or the tbi bottom half? Help me out and I'll get that knocked out.

I also grabbed some whole knuckle outer hub assemblies from a Rodeo for the Big Brake conversion. What's just as important as going? Stopping!!
Not positive I will run those junkyard rotors though. For the money, I think a complete front end rotor and caliper package from rockauto is going to look real good and stop real good too for the coin.
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As for the white and gold/bronze 88 Trooper. It is almost done. I sent the pwr steering pump off to rebuilt only to get denied and now need to find a replacement for it, pulley and all.
It seems the 88 is a cutover year where Isuzu switched to a spline drive pulley and cardone won't rebuild mine for whatever reason. So I'm hoping to switch to the new style with a spline pulley.
Last tidbit on the 88 I did was upgrade the front disc and caliper to the dynamicFriction special rockauto has right now. Ceramic pads too. Repacked the bearings and am going to put gold painted Aisins on it. Need to put the new clutch line in place with a new master and slave. Seems she bled out when I was on vacation. Once that is done, then she is for sale. I'll post a pic of the beauty when I'm done.
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last little teaser.... I have an awesome surprise coming out of Atlanta for wheels. Just you wait!
I will get on the Black LS here soon!
 
#22 · (Edited)
I used a 1991 pickup 3.1 flywheel (same part no as 2.8, so either/or is fine) and 3.1 clutch kit on my 3.4 (just checked my rockauto receipt from 2015).

Regarding ECUs and injectors in a 3.4:

2.8 ECU + 2.8 injectors = fine at idle, lean at WOT
3.1 ECU + 2.8 injectors = fine at idle, may need fuel pressure turnt up to keep up at WOT (heavier spring for an additional psi is available)

2.8 ECU + 4.3 injectors = can be rich at idle, fine at WOT
3.1 ECU + 4.3 injectors = likely to overfuel at idle and WOT

It will likely depend on how hopped up the motor is. An untouched essentially stock 3.4 may do fine with just the 3.1 ECU and the 2.8 injectors. Cam upgrade and some other stuff may require adjustment or jump to the 4.3 injectors + 2.8 ECU combo plus additional fine tuning.
 
#23 · (Edited)
What Paul said, if you order the flywheel and clutch kit for a 1991 3.1 4WD pickup, you can't go wrong. The 3.4 should run better with the 3.1 ECU. I've been running my 3.4 LS for years with the OE 2.8 ECU and a Holley Big-Bore TBI, which does pretty much the same as a GM 4.3 TBI. Haven't had any big issues with it, although I do have a spare 3.1 ECU ready to go if need be.

Each swap is gonna be a bit different on tune, depends on what you do for exhaust, how you build the engine. As Paul was saying a heavier spring (14 psi spring) in the fuel pressure regulator will fix most ills with the swap. If you use 2.8 injectors you're definitely gonna have to increase fuel pressure; a 3.4 on 2.8 injectors will "lean surge" when cold. Having more fuel pressure/fuel injected will cure the lean surge, and when the ECU goes into Closed Loop it's regulating with input from the O2 sensor and should be OK except as Paul mentioned might be lean at WOT.

Conversely, you may run rich with the 4.3 TBI and bored-out intake, depending on the build. In that case you might need to reduce fuel pressure. Just a tuning thing. The stock regulator can be made adjustable within a few-psi range, and that could be enough to make the engine happy. I tweaked on the FPR when I did a "3.2 Stroker" build back in 2005 and it was just right, killed the lean surge and had good fueling all-around.

Use the stock 2.8 intake manifold, that's what you'd need to ship off to have bored to fit a larger TBI. The best mod (besides exhaust) that you can do to these engines. They respond well to increased airflow.

You've been busy, have fun!..........ed
 
#24 ·
One other thing that will likely help in any condition is swapping to a heated o2 sensor. Geoff had a writeup on his site. I know mine will not go into closed loop at idle no matter how long I let it sit, even with the o2 sensor sitting in the cat directly where the 2 exhaust downpipes enter. I have to actually drive it for that thing to heat up enough to go into closed loop. If I end up keeping my motor longer term it will definitely be on the to do list.
 
#25 ·
Both you guys are super immensely helpful. Thank you.
So after your message @Ed Mc. I looked around some yards and there are tons of Astro 4.3 TBs.
I got one for $50 complete.
I think what you were saying too is the throttle plate on that ebay one looks identical or similar to the 2.8.
Well check this out. yeah its dirty but little elbow grease and she's new again.
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#26 ·
Duder where's another Astro TB?? I am thinking of swapping back to the GM TB and huckin' the Holley and it's sticky injectors.
 
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