Isuzu SUV Forum banner
1 - 15 of 15 Posts

·
Registered
Joined
·
116 Posts
Discussion Starter · #1 ·
I read a lot of posts with various problems with the 3.2 and later motors, yet the 3.1 in my '92 Rodeo just keeps plugging along. I've chased a perpetual EGR issue, which never shows until we take a longer trip, but even then, it has never seemed to affect how it runs. Engine-wise, I've had to replace a few distributor caps and plug wires, a couple fan clutches, one Idle Air Control valve, thermostat and a few other minor things, and chased a few coolant and oil leaks, but it's never needed more than occasional topping off of fluids. Burns less than a quart of oil between changes. Only one O2 sensor, changed once. Pre-OBDII, so not much info for codes, but maybe also less to go wrong?

It has a timing chain, not a belt, still original at 140k. Throttle-body injection, pretty much conventional distributor and single spark coil, so no balky separate injectors or hi-tech ignition system to troubleshoot. Open the hood, you see the motor and an air cleaner like on my old '67 Ford Falcon, not all those glitzy add-on coverups and bulky intakes, hoses, wires and what-not. I get overwhelmed just looking at the pics of the newer engines! :shock:

It was pretty gutless since we've owned it, till I finally had to replace the old exhaust with a slightly upgraded one with free-flowing cat and muffler. It was like setting it free, it had a lot more power and snap ever since that one change from stock. It might be the lowest HP of the various sixes found in the Zu's, but it does the job for me.

The rest of the vehicle has been dependable as well, but it's getting worn out and rusty after 21 years of dirt, mud and snow. We've sunk far more money into keeping all that up than we ever put into the motor itself. Still, it's been very cheap to maintain, considering the years of use and abuse. Getting things diagnosed is another thing, nobody around here seems able to troubleshoot stuff and just wants to throw parts at it, so I do most all the wrenching myself, same as on my other rigs. That way, I know what's done and how well.

I just don't see much here on the ol' 3.1. What's other people's take?
-Ed
 

·
Registered
Joined
·
7,076 Posts
The 3.1L and 3.4L V6's are great motors. Mechanically identical other than the bore size. The 2.8L was the same but it had an aluminum bodied oil pump that seemed to wear out and take the motor with it. So they were not as reliable as the 3.1L and 3.4L which had all iron pumps and improved crankshaft oiling. They are one of the best and most used Chevy V6 engine. Their production run lasted 30 years so there is lots of parts and support. One day I wouldn't mind a late 90's 3400 engine in the trooper. I have been contemplating 14:1 compression and propane too. But for now my rock solid 3.1 serves me well.
 

·
Registered
Joined
·
2,969 Posts
I built a 3.1 for my Trooper based on Goeffs, one tough engine, but it started loosing oil pressure after a few years, so I figure I did something wrong. But it was running great until then. I am now in the process of putting a 3.4 in my Trooper, might get it fired up today. Took it from a 95 Camero. I have had several of the 4 cylinders also but like the v6 better.
 

·
Registered
Joined
·
755 Posts
Just finished building a 3.1L for my '89 LS Trooper "Obi-Wan", and must say that I'm tickled with the results. The original 2.8L in mine had spun a rod bearing and #3 connecting rod had about 1/4" of slap in it (video to come). I pulled a transverse-mounted 3.1L from a '91 Pontiac 6000, which already had the starter mounted on the correct side. This engine only had 131k miles and was taken to pull-a-part because of a simple blown head gasket. Swapped '92 Camaro 3.1L iron head pistons into it, since the original engine had aluminum heads and deep-dish pistons. Also upgraded the cam to the Comp Cams 252 kit, but opted to use the original rocker arms to save a little bit of money (next time, I'll go ahead and order the whole kit with roller rockers). Did the smog pump delete. Bored the intake manifold to 1 3/4" and installed a 5.7L throttle body with 4.3L injectors. I upgraded to the larger diameter Exedy clutch and pressure plate from the '91 Rodeo (4WD only!!! 2WD clutch and plate won't work). Had a local shop install true dual exhaust all the way back. Purrs like a kitten and pulls like a tractor! I don't know if anyone else has used an engine from a transverse-mounted application, but I didn't want the hassle of redrilling the block to mount the starter on a 3.4L pulled from a Camaro. This could potentially open up a whole new possible source of good, low-mileage, reliable engine blocks, as they can be bored out to match or come close to a 3.4L with very little additional cost and effort. The pistons have to be swapped anyway, due to the difference in dish profile and the need to bump the compression up to cast iron head specs. I'll put pics up when I can.

EDIT: Started a new thread to document progress here. V6 swap
 

·
Registered
Joined
·
2,969 Posts
You got me curious on the throttle body, I have never heard of anyone using a 5.7 throttle body, it is usually a 4.3 with 3.4 injectors. So this may be another avenue.
BTW that is an impressive list of Isuzus!
 

·
Registered
Joined
·
7,076 Posts
The 4.3L 5.0L and 5.7L all used the same throttle body. So it does not matter where you find it. Just find one with a tight throttle shaft. I like using the later model cores because they all have the bolt holes for the throttle cable bracket.

The Isuzu version of the GM V6 is actually a Lumina Van engine with an S-10 intake. That is the easiest easiest way to describe it.
 

·
Registered
Joined
·
2,969 Posts
Thanks Geoff, I did not know that information.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #8 ·
Great responses, thanks! I didn't know any of that myself. Really only that it was a GM motor, maybe built in Canada. I'll probably never do any of those swaps or upgrades, but very interesting nonetheless.

kg4miq, I'd be curious to hear any subjective or measured performance gains of your rebuilt 3.1.

I'm still used to gauging engine size by cubic inches, I was a bit surprised that the 2.8 is only 170 cu.in., the same size as the straight six that was in my 1967 Ford Falcon. The Falcon 170 with three-on-the-tree was real dog for performance, but steady and dependable with good gas mileage. Even the 3.4 is not much over 207 cu.in. and the 3.1 is quite small at 189 cu.in.

The 225 Dauntless V6 that was in my 1967 Jeepster is significantly larger, and I thought that was a pretty small mill, producing about 200 hp and 225 lb/ft torque. But with that long stroke, it could sure pull like a tractor and sounded like one too, lugging up a hill in second gear, which it could do all day without a hiccup. It still sounded good and ran great when I finally sold it, but the rest of the vehicle needed basically a frame-off resto and rebuild. Kinda like my Rodeo, except for the lugging tractor-pull part, lol!

-Ed
 

·
Registered
Joined
·
755 Posts
I'm still using the original 2.8L ECM to control the timing and injector pulse, but the gains are definitely noticeable and worth it, for the cost.

Round numbers -
Engine: $225
Pistons, bearings, rings, bushings, etc.: $250
Camshaft kit: $300
Throttle body and injectors: $40
Motor mounts: $60
Cost to bore intake: $40
Cost for machine shop to clean block, rework heads, install cam bushings and freeze plugs: $200
Total: $1115

I "feel" like it has more get-up-n-go than any other first-gen V6 Trooper I've driven (although, I haven't driven Jerry Lemond's supercharged beast, yet). Can't say that I've actually put it on a dyno yet, but I can chirp the tires in third gear (the kid in me giggles when this happens). Definitely opened up some horsepower and torque. Haven't run it enough yet to get a feel for fuel economy, but that will come later, as the engine goes through the break-in period. I built it with daily driving and trailer towing in mind.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #10 ·
You could easily drop that much coin and more into a crate engine or shave a couple hundred off your cost if the rig already had the basically running 3.1.

I always knew the stock 3.1 was operating at far below its potential. Especially when I saw the improvement of better exhaust flow. I didn't even upgrade the throttle body's air filter from stock, which would let it breathe even better. Mine might not lug like a tractor, but it does love to rev! Maybe factory "undertuning" equates to engine longevity, or helps it to meet emissions, I dunno. I always thought a stronger-running motor would be more efficient, able to "loaf" more of the time instead of struggling to keep up with traffic or pull a hill. I'd generally have to floor it or shift down to get any chance at passing someone on the highway, for example. As a result, I often opted to slow down and stay behind someone, just because it took a forever stretch of clear road to safely pass, even on interstate.
 

·
Registered
Joined
·
7,076 Posts
The worst thing about the TBI motors was weak cams and low compression. This is true for the V8'S too. If you can get compression closer to 10:1 and get the much healthier cam it really wakes up the motor. More so than external bolt ons that's for sure.

I never had time to CC my engine but from rough calculations I am just over 9:1 compression with mildly ported heads and gasket matched ports and intake. With the comp 252 cam it has lots of grunt to 5500 RPM and I can rev to 6000 if I feel like it. But I built the engine for off idle torque and it does that very well. My 2.8L was fine on the road with 33's. I even had it pulling my utility trailer on some serious highway hills but I was down in 2nd at 4000RPM. With the motor I have now it hauls even more weight in third up the same hill and I usually sit at 3500 RPM doing 50MPH up the hills. I can go faster by tipping into the gas but I don't like winding it out for that long even though I'm confident it can take it.

Thhis engine family take a lot of hate because early 2.8Ls used to spit main and rod bearings and they made even less power. However once they were ironed out they were as reliable as a nail. But they still took crap for being low on power. But feel free to point out to anyone that they made more hp per liter than any of the V8'S offered at the time.
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #12 ·
Good real-world observations, Geoff. I guess my "stock" 3.1 bears out that low-compression, I never measured much over 160 pounds in compression tests, maybe closer to 130-odd pounds. I think I have some old tests written down somewhere. What's stock compression ratio? Something like 7:1? Yet the owner's manual suggested burning premium, though we usually burned regular anyway, but it sure did used to rattle the valves under load. Oddly, it quit doing that after the exhaust upgrade, or something else I'd done along the way with normal parts replacing/repairs.

Also as you noted, raw hp makes for a good advertising spec, but it doesn't mean much without a torque curve to match. The hp has to be there over a wide rpm range to really do any good, for us offroad types, higher hp at low rpm= :smile: !
 

·
Registered
Joined
·
116 Posts
Discussion Starter · #14 ·
Thanks, I was just being too lazy to go grab the owner's manual. I happened to be closer to it today :) so I looked it up. 8.5:1, the 2.6 is 8.3:1. According to Edmunds, it produced the same HP as the 26, a meek 120hp. Torque wasn't listed, but stated it had 30 more lb/ft than the 2.6. In '93, the new 3.2 made a stated 175hp, quite a bump up. http://www.edmunds.com/isuzu/rodeo/
Now I'm tired from all the exertion, and must rest. :lol:
-Ed
 
1 - 15 of 15 Posts
Top