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Bone stock 1989 Trooper S 2.8.
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Discussion Starter · #1 ·
I was driving my wonderful trooper the other day to test my tire balancing skills, when it suddenly gave a mighty backfire, shudder, pop - and died. I was able to pull over, but it refused to start. With 260k miles, I assumed it was something in the ignition (which the PO had "fixed").

By the time I got back to the rig, someone had bashed out my window to get an almost dead battery - and the brand new, still in the box, tow bar in the back. After ANOTHER day of driving all over North Carolina to get another bar (they seem to be very hard to come by right now), and towing the rig home, I started on the engine.

My first mistake was "assuming" (you know what that means) that it was the timing chain. Again, with that many miles, I figured it probably needed a new one even if it wasn't the culprit. So I started on the front end.
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OMG, the grease! Clearly, the front main seal has been leaking, I dunno, since the mid '90's? This pic is AFTER the first dose of engine degreaser.

Sadly, the timing chain was not the culprit. While loose, it clearly didn't skip a tooth. In my defense, I checked the rotor while I turned the crank and there was a LOT of slack.

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Then I did what I should have done in the first place and pulled the distributer. Now I know why I prefer the 2.6 I4: Who the heck thought that was a good place for the lockdown bolt?!?!?

Finally! The smoking gun:
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A new distributer and a good oil change is no problem, but... WHY? Just high mileage? Or a miss-matched gear? I vaguely remember back in the day there were chevy (I think) engines that could take two different distributers, but the gears were a different cut and would soon self destruct if you picked the wrong one.

It hasn't been a complete waste of time. The front main seal clearly needed replacing (I got an extra by mistake, anyone need one?), and the water pump had just the tiniest bit of play in the shaft, so I got a new one.

The exhaust manifold gaskets are - literally - missing, so that's on the list as well. And two of the bolts are either broken off or missing. Pretty sure I'll have to drill out the head.

And I want to ditch the ugly clutch fan and put in an electric one that I've had sitting in the basement for 10 years.

All this happened the DAY AFTER I made my reservation for the fall Uwharrie trip, and got a full set of new mud tires. Figures, right? I still have a couple months. Should be back on the road by then.
 

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Bone stock 1989 Trooper S 2.8.
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Discussion Starter · #2 ·
One question: How accurate is the oil pressure gauge in an 89 Trooper? Because it regularly says I have over 100psi of oil pressure, and never goes below 50, even at a hot idle. I assumed (there's that word again), that the gauge - like the temp gauge - was off due to the gm engine.
 

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Bone stock 1989 Trooper S 2.8.
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Discussion Starter · #4 ·
Okay, good. One possible cause for a sheared gear is too high oil pressure. So maybe it's just 260k being a lot of miles on a 80's GM engine.
 

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That's a lot of oil pressure! As you say, it certainly would put more strain on the gear, with the pump pumping away that hard. However, it also could just be due to wear. How is the camshaft gear? It of course is a lot harder than the aluminum. Unfortunately, no way to check now until you get it back together and running. You can install a manual gauge into the port where the oil pressure sender is installed, to verify oil pressure.

I can't imagine 100 psi, though, the relief spring in the oil pump would pop with that high of pressure. What brand of oil filter are you using? You can install a larger filter meant for a GM 4.3 V6, it will give you more oil capacity. I use a Wix 51036 or NAPA Gold (made by Wix) 1036. They'll go right in easily, from the wheel well side. All you need to do is pull the rubber splash guard up for access to the oil filter.

If indeed it's running that high of pressure, I'd be checking the oiling in the top end to make sure everything is being properly lubricated. You may have some plugged oil passages. BTW my 3.4 runs around 50-55 psi above idle, and nowadays it drops to maybe 35-40 at hot idle. My 1st 2.8 Trooper was pretty much the same, even with over 160,000 miles on it.

It should run a lot better with a new timing chain, for sure! That one is quite stretched. Be sure to replace the timing damper as well.

Be aware that when you have the timing chain set aligned, #4 cyl is on TDC on the compression stroke. So you'll want to install the distributor with the rotor pointing at #4 cylinder. And the ESC (Electronic Spark Control) wire inside the center console must be disconnected from itself when checking/adjusting base timing.

Here's a few distributors at Rockauto.com:


IDK if you can get just the distributor drive, it is replaceable. But the dist has a lot of miles, anyway, so it might be a good idea replacing it anyhow. Rebuilt & new ones aren't that $$pendy.

FYI, according to this site the P/N for the gear is 01985769:

Distributor, Distributor Parts The gear, however is discontinued. May still be available from old stock online.

Re the nasty oil/grease muck, I've had good luck with any of the Purple Power type of cleaners, they seem to cut thru the stuff pretty well. Just don't let it sit on aluminum parts for too long, it's alkaline and will start to etch.

I bought my '90 LS years ago with a busted timing chain, and after finishing the replacement I wrote a How-To while it was still fresh in my noggin.

If you'd like that article, send me a Private Message (or Correspondence, or whatever the new format calls it), with your email address, and I'll forward a copy to you.

HTH & G'luck with the repairs...........ed
 

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Welcome to the board! I'm about 2 hours from you, southeast of Raleigh. Since you are doing so much front end work, and within your budget, replacing the radiator, tensioner, and harmonic balancer might be a good idea as well.

So great to see Ed Mc still around as well! He can confirm, but I think once all is back together, you'll be looking for 12-14 deg advance on the timing.

Unfortunately, dropping the oil pan without dropping the front differential is not an option, but the concern is how much debris from that dizzy shaft is running around the block.... :oops: It might take several oil changes and some magnet magic to pull the fragments down and then out......unless Ed has some ideas.
 

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Welcome to the board! I'm about 2 hours from you, southeast of Raleigh. Since you are doing so much front end work, and within your budget, replacing the radiator, tensioner, and harmonic balancer might be a good idea as well.

So great to see Ed Mc still around as well! He can confirm, but I think once all is back together, you'll be looking for 12-14 deg advance on the timing.

Unfortunately, dropping the oil pan without dropping the front differential is not an option, but the concern is how much debris from that dizzy shaft is running around the block.... :oops: It might take several oil changes and some magnet magic to pull the fragments down and then out......unless Ed has some ideas.
Howdy Don! Been a while!!

I was thinking that the gear was aluminum but maybe you're right, if it's steel, I suppose a magnetic drain plug might pick up the shards.

Otherwise as you suggested, it might just be a thing of changing the oil and filter a few times. The engine has so many miles on it, that one could hardly justify tearing into it unless it's for a rebuild.

At that point, might as well install a 3.1 crankshaft and RWD 3.1 pistons, and turn it into a "3.2" (3.1 with an overbore). The "Stroker 3.2" runs great and has a nice jump in torque and hp over a stock 2.8. Even more so with a Comp Cams "252" "torquer" grind.

Cheers.........ed
 

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Discussion Starter · #8 ·
The last of the parts should be here today. I couldn't find a gear I was confident was the right one, but I found a Cardone rebuilt dizzy for $30 that comes with the ignition module. Done deal.

The dizzy gear is iron, but very soft so it's a sacrificial part. I just couldn't see wasting time on trying to save $10.

I also ordered a LOT of engine degreaser.

I was really happy that I was able to remove - without breaking any bolts - the driver's side exhaust manifold. Couple of them were already loose. There was no gasket. I can't work on the passenger side until I put the front end back together, since the AC and Alt are flopped over on that side. I'm hoping that the missing bolts on the that side are just that - missing - and not broken off.


My radiator looks okay, although I have to solder up the bracket on one side. Actually, it LOOKS terrible because the radiator cap has been leaking for probably a decade. I'm in the process of fabing up a shroud adapter for my electric fan. I detest clutch fans.

More pics tonight!
 

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Discussion Starter · #9 ·
Don B, are you the guy parting out the '90 on Craigslist? I thought the listing was down your way.
 

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Hi Ed!

No, not the one parting out. Mine's a '91, and still running great, just the rest of the stuff falling apart/rusting.

GM never used gaskets on those exhaust manifolds but it is a valid question how ISUZU received the engines from GM and whether manifolds were already installed and the which entity decided to install gaskets or not. Mine had several snapped bolts and so I had a couple of different exhaust leaks, 15 years ago? Luckily I ordered new replacements from our ISUZU parts supplier at the time, BUT a couple of those have accessory extensions so that's a trick to replace. The broken studs easily came out once the manifolds were off. Most go ahead and add the gaskets during the renewal process. The manifolds are ISUZU specific to accommodate for the reversed starter location so manifold replacement is a hassle. Indeed, as I'm writing this, I remember now having to replace the driver side manifold because one of the ears were broken.
 

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Discussion Starter · #11 ·
I'll be honest, I've never heard of an engine without manifold gaskets. WEIRD! I ordered a set anyway. Can't hurt.

I should know late Sunday if I've got broken studs or not. The missing bolts are just that - bolts. No accessory mounts, thank goodness. Passenger side rear bolts.
 

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Discussion Starter · #12 ·
Well, the new timing chain is in, and the engine buttoned up except for the dizzy. Then the cleaning began. Some parts were smooth because all the pockets were full of old gunk. Some places almost an inch thick.
I went through 2 cans of engine degreaser, but with a lot of scrubbing, I can actually see metal again!

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Only thing that bothered me was the fit of the new timing set. I’m used to a new set being so tight it’s hard to install, but this set was very sloppy. Not as bad as the one that came out, but I’m not happy. You can see the slop in the pic.

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Tomorrow, I’ll finish up the front and start on the exhaust manifolds and valve covers.
 

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Yeah, that chain seems quite sloppy. Did you notice any play in the camshaft or crankshaft? It would have to be an awful lot to affect free play. Maybe it's just a not-so-good chain. As I recall the timing set I had for my 3.4 was quite tight when I installed it.

Well, you should be able to at least get the base ign timing set. Worst case the cam timing will be retarded a hair, which will give you less low-end torque and higher top-end performance. My old 2.8 with a quite-stretched chain revved quite freely to 6000 rpm. It did have some horsepower-adders, though.

Looks a lot cleaner, at least you can see the engine now!!

Let us know how it runs.........ed
 

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Discussion Starter · #14 ·
Well, got everything back together and fired it up today. OH MY GOD, WHY IS IT SO LOUD?!?!!!

I guess the punks that stole the crappy battery also wanted the crappy aftermarket catalytic converter as well.
Gosh, that sucks. But did they have to cut it out and do the most possible damage???

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Yep, that’s right - they managed to hit BOTH the “T” pipe AND the O2 sensor! Since the tailpipe was already shot, I’m just going to have the local shop replace the whole thing. Maybe get a “Y” joint instead of a “T”. The inefficiency of that thing makes me shudder.

But the engine ran great once I got the timing close. I think I’m a tooth off on the distributer, but there’s room enough.

I haven’t timed it yet because the radiator isn’t in. This week I’ll be fabricating a shroud adapter for the electric fan.

I chickened out on the passenger exhaust gasket. It’s a nightmare over there. I also put off the leaky valve covers. I’m tired.
I have to say that I’ve never hated an engine like I do the 2.8. GM clearly didn’t understand the metric system in 1989.
 

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Discussion Starter · #15 ·
Electric fan was a total bust. Somehow, I was off 1/2 inch on the depth, and didn’t have enough room. Booo!

And I’m not sure how they did it, but they also managed to ruin my alternator. Either that or it died while on the table. Who knows.

Going to build my own exhaust, I guess. Local shop wants all my money PLUS a pint of blood. 🤑
 

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Well, don't that suck! A few years back we were having a birthday party for my Daughter at the Cheesecake Factory in the Tacoma Mall. When we came out, someone had cut the cat out of my Brother's T100. He had to drive all the way home with the ear-splitting exhaust. Fortunately they didn't do a lot of damage, and I had a new cat that was supposed to be for the Trooper, but I went a different way and didn't need it anymore. A little fitting and welding, and his truck sounds better than ever!

Your observation about the restrictive exhaust is right on-the-mark. I re-did mine and the difference is like night and day. If you use a cat with dual 2" inlets, you can plumb the 2" downpipes from the engine directly into the cat. It's a bit of cutting and fitting, but do-able. The pssgr's side you take back to the 1st flanged joint, and use a 90-degree pipe. On the driver's side, just extend with a few mild bends to get to the cat, and you've got it!

The cat I used has a bung for the O2 sensor right in the case. So the sensor will warm up faster and run hotter than it did in its previous location in the exhaust wye. The engine will go into Closed Loop faster and run cleaner.

Walker 15022 cat: walker 15022 | eBay

The price has gone up about $100 since I did my project. There are less expensive ones out there, too, that should do the job as well. Such as this $55 cat with dual 2" inlets and a single 2-1/2" outlet:


I'd recommend a tailpipe diameter of no more than 2-1/4" for an otherwise-stock 2.8. Any larger and you'll lose a lot of low-end torque, and these don't have that much to begin with. You can use a 2-1/2"-to-2-1/4" reducer on the outlet.

I had a 2.5" tailpipe bent and installed for my 3.4 LS and it's just right for that engine. For a 2.8, even a 2" exhaust would work wonders over stock 1-7/8". Had a 2" cat-back exhaust on my old 2.8 Trooper, with a cheap generic turbo muffler, and it ran and sounded good.

The 3.4 has a nice growl at low speeds but isn't noisy or boomy down the hiway. I'm using a Dynomax Super Turbo muffler.

Here are some 2-1/4" 17747 Dynomax's on eBay for as low as under $56 shipped:


Hey, at least it's running! How's your oil pressure, still astronomically high? If so, you'll have to do the check with a mechanical gauge to be able to rule out an internal issue.

HTH & Keep Up the Good Work!.........ed
 
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