Isuzu SUV Forum banner

3.4 Rebuild and Swap - 90 Trooper - Noob alert

2501 Views 76 Replies 6 Participants Last post by  Ed Mc.
ALRIGHT so I've had my 1990 Trooper for maybe 6 years now. She's got around 165k mi. Here she is in all her glory:

Wheel Tire Cloud Sky Vehicle

The oil pressure has slowly been decreasing over the years. It's now sitting at about 12 psi at idle while warm. Relays clicking and clacking under the dash and under the hood. I only found this out after swapping the 3 center gauges for Autometer gauges that actually provided useful info.

Here's a link to the thread that led to this thread

In any case, Ed helped me find a 3.4 long block. Thanks Ed Mc!

Motor showed up at my work, I brought it home, turned the crank, no joy. Seized. So I started tearing it apart. I figured I'd need to rip it apart anyway. Thinking the worst, I paid no attention to which pushrods/rockers went where. If figured I'd eventually just replace all that anyway. In any case, I found the culprit!

Motor vehicle Automotive tire Gas Circle Fixture

Looks like someone had dropped a torx bit in the cylinder. I'm hoping this was done AFTER the donor vehicle was parked for salvaging. The head shows no signs of impact from this bit. I did try cranking the crank with my big Makita impact, however. I don't think it did too much damage though since it just tightened the bolt on the crank.

Here is a photo of the deck ( gasket still on ) and some reference photos of the cylinder walls

Automotive tire Automotive lighting Motor vehicle Automotive design Automotive exterior

Automotive tire Tableware Fluid Wood Automotive wheel system

Grey Wood Water Tints and shades Horizon

Looks like there's still some crosshatching and I don't see any gouges. The water jacket is rusty as heck, though. I'm trying my best to avoid sending this to a shop.

My next steps is to degrease the entire motor, get my machinist's straight edge to check the deck for flatness, check my heads for flatness and then rip off the oil pan to check bearings with plastigauge.

My question is, how should I go about cleaning the water jacket? There's so much rust and stuff in there. I don't have access to a powerwasher nor a spout for water. I'm using just spray bottles and catch trays to clean right now.

Any advice?
See less See more
  • Wow
Reactions: 1
1 - 20 of 77 Posts
Douse it all with muric acid or aluminum hydrogen fluoride. Scrub where you can then rinse with plenty of water.
  • Like
Reactions: 1
I've been using Zep floor stripper in a spray bottle. I use it to degrease whenever I work on oily stuff. It IS stripping the paint off the oil pan but I'll be repainting it anyway.

Is it safe to spray cleaner in the coolant passages? My only concern is getting gunk stuck in there.
An inexpensive garden sprayer might give you a bit more washing power, lacking a higher-pressure supply of water. Not much of anything that's safe for you to handle will hurt a cast-iron block.

Do be careful if you use muriatic acid, as it will eat up aluminum (such as the pistons!). It'll sure clean the Heck out of cast iron or steel, that's for sure.

Hard to tell but are there any wear ridges at the top of the cylinders? If not, then it's a good candidate for a re-ring. The pistons don't look like they're abnormally carboned-up, just the usual. So it's likely not an oil-burner.

If you are going to take it down that far, you could just have the block hot-tanked. Then you'll get new cam bearings and freeze plugs. Otherwise clean 'er all up and inspect everything.

Before you tear the valves out of the heads, spray some carb cleaner down the intake and exhaust ports and see if any fluid leaks out of the valve into the combustion chamber. You'll need to give extra attention to the leakers. Or just send the heads in for a valve job. But if it all looks good, you could just clean up the valves and lap them in with fine valve-lapping compound.

Plan on replacing those nasty-looking lifters for sure! I'd imagine you'll want to put the Comp Cams "252" kit in there. I certainly wish mine had that! When you remove the old cam, wipe clean the cam bearing bores and check all the bearing inserts for scuffing/wear. Same with all the main bearings and rod bearings. This is the time to renew if they look marginal. And they really aren't that expensive.

Note that the bearings towards the front of the engine are the farthest away from oil pressure and typically will be the 1st ones to show wear if there's an oiling problem. So pull the front main and a rod bearing towards the front and that will give you an idea of what to expect when you inspect the rest of them. If they look good, likely the others will, too.

Anyway, off to a good start! Keep us posted.........ed
See less See more
  • Like
Reactions: 1
I didn't feel any ridges on the tops of the cylinders but I'll need to 2x check. I dropped by local head repair shop today and they quoted me $50 to hot tank the block and heads. Another $40 to install cam bearings. Valve job is $200, though. I'm not sure how far I'm willing to let the shop go. I do want to do some of this work myself. I'm even debating on having the shop hone the cylinders.

Yes, I will be following your advice with the 252 cam. If this thing fails SMOG... well I'll just cross that bridge when I get to it. I do still need to pull the bottom end and check the crank bearings. Lots of Christmas-ey stuff to take care of this time of year so this may be a slow project.
If there's no ridge on the cylinders you're good, if just a little ridge all you need to do is use a ridge reamer. Then just rent a ball hone from Autozone etc and deglaze the cylinders yourself. Use a spray bottle with Marvel Mystery Oil as a lubricant, and check YouTube videos for an idea of drill speed and how fast to go up-and-down with the deglazer. All you need to do is provide a good new surface for the new rings to bite into for break-in.

As I was saying on the heads, if the valves are still sealing well, and you find the valve faces aren't pounded into the valve seats, you can clean everything up and lap in with a suction-cup lapping tool and fine valve grinding compound. Check a cleaned, oiled valve in a cleaned valve guide for slop. There should be very little to zero slop when you wiggle the valve stem to and fro in the guide.

Check heads for straightness and if all looks good, reassemble with new valve stem seals on the intakes and the rubber O-ring style "umbrella" seals on the exhaust valves. Be sure to keep the valve, springs, hardware together and return to their original position, if you end up re-using them. One way to do that is to label them "1-E", "1-I", "2-E", "2-I", etc. Keep the springs/hardware in an egg carton with each space marked. Of course, if you're going to do the cam kit that won't matter. Except for keeping track of where the valves go. You can stab them into a chunk of cardboard and write the position of each in Sharpie/Magic Marker.

Your shop sounds very reasonable on their charges, so that's a good thing. And it sounds like you have a decent core engine. Inspection of the crankshaft and bearings will tell all!

This last one, you could probably make your own valve spring compressor with some sturdy flat bar. Or weld up something really fancy!
Cylinder Font Engineering Gas Parallel
See less See more
  • Like
Reactions: 1
Prices certainly sound fair. Personally, I'd have the shop do the cam bearings and hone the cylinders as having the right tools makes a difference and these are easy to screw up. The valve job is not particularly difficult, just tedious and time-consuming, thus the price. Ed's advice on the valve job is more than solid if you decide to DIY that part.
  • Like
Reactions: 1
I think I'm going to go the minimalist approach (when it comes to relying on a machine shop). As per Ed, I'll check for leaks on the valves. If they need to be re-done, I'll order new valves and seals and lap them myself.

The block definitely needs to go in for a hot tank. The rust in the coolant passages is really bugging me. The cylinders don't have a lip. I'll borrow my buddy's ball hone and hone them. I'll probably have to buy a smaller hone to hone the lifter passages.

I'll most likely be getting my parts from DNJ. They seem to be pretty reputable.

So far on my shopping list

DNJ Re-ring kit (head gasket set, lower gasket set, main bearings, piston ring set, rod bearings
Timing chain kit with new guide
Oil pump
Freeze plug kit
valve stem oil seat set
Water pump

I'm still uncertain about changing the cam bearings. Is this necessary? Are there tolerances to test for or is it a visual inspection to look for wear?

Also uncertain about which cam to go with. I know the 252 is the best bang for your buck while still being able to pass SMOG ( probably )

I was looking at Comp Cam's website and I'm kinda scratching my head over it. Is this the one I need? Saves me fromt having to buy a separate timing chain kit and new lifters.

Also, for rockers, should I be going to roller rockers? Or should I just re-use my old rockers and push rods?

Sorry for all the questions. I lost motivation over Christmas weekend but I sprung right back up as soon as I had to drive the Trooper. I just kept thinking about how much quicker the thing could be! This is my first real build, however. I've done custom turbo installs and I've rebuilt tiny 2 stroke motors but I've never tackled anything like this.
See less See more
  • Like
Reactions: 1
The kit you referenced would work, but you do need to have the performance valve springs and retainers. The Full Kit has all the stuff in the "SK" (i.e. "Small Kit") and also includes performance springs, retainers, keepers, and valve stem seals. Here's the link at the Comp Cams website:

They say "temporarily out of stock" but you could piece-out the kit or just wait until back in stock. Summit Racing also carries Comp Cams parts:

Same price as the Comp Cams website, and they're showing a ship date of Feb 6, 2023. The pic at their web **** shows exactly what parts are in the kit.

The valve springs have to be upgraded, because the stock springs will coil-bind when used with the higher-lift cam. Note that early Z28 valve springs and keepers are also compatible with the cam kit, so you might be able to source them separately. These springs require specific retainers.

Summit has the Comp Cam springs for the V6 available to ship now:

They also have the retainers available separately:

Rather expensive, you may find generic LT1 parts cheaper, IDK.

The valve keepers would just be stock items you could buy at Summit, Rockauto, eBay, etc.

If you're going to get the block hot-tanked, the caustic solution will eat up the cam bearings. So you gotta get new ones anyway. IIRC machine shop quoted $40 for those, that's quite reasonable if that includes installation. I'd leave that bearing R&R to the pro's, BTW.

Cool you have access to a ball hone, it doesn't take much to put a decent cross-hatch in the cylinders with one of those. I find Marvel Mystery Oil makes a great lube for honing and it smells great, anyway. If you do the deglazing after you get the block back, be sure to Scrub Scrub Scrub the cylinder bores with Hot water and a bristle brush (a round toilet bowl brush works great) until a white paper towel sprayed with WD comes back clean when you wipe down the cylinders. Otherwise the abrasive works into the x-hatches and causes extreme wear to the rings. Remember, Hot, Soapy water, that's the trick. I like Dawn but whatever your preference.

For rocker arms, you can get a nice bump in performance by using Comp Cams 1.6:1 roller-tipped Magnum rocker arms. The stock rocker ratio is 1.52 and the 1.6:1 ratio increases lift slightly and also a bit of duration as a result of the increased lift.

Rather expensive at $170.95, you may find generic LT1 parts cheaper, IDK. These have gone up about $100 in 20 years but what can ya do, inflation is rampant! IHMO still worth the $$$.

The roller tips reduce friction on the valve stems, and hence lessen valve guide wear, reduce oil temps and give more HP. With the use of performance valve springs, the added lift should work just fine with the 252 cam. I've gotten away with using them in my rigs without changing the valve springs, but combined with the cam you do need the performance springs.

Note that any generic Small Block Chevy V8 Non-Self-Aligning roller-tipped rocker arm will also work. I've been running a set of cheap eBay V8 rockers in my 3.4 for over 20 years and they seem to work just as well as the Magnums I used in my old 2.8 Trooper. But the Magnums are very high-quality pieces, you can tell when you look at them. Of course even the "cheap" V8 items aren't probably too cheap on eBay anymore.

Note, if you use V8 rockers you have to use the V6 rocker balls. V6 heads use a 10mm rocker stud; the V8 rocker studs are typically 3/8" or larger. But the body of the non-self-aligning rocker is identical.

Here's a generic set of V8 rockers on eBay for around $107 shipped, that looks decent:

You'd have to use V6 rocker balls and also V6 locknuts on these. Just get generic V6 items, I looked up the rocker balls at Rockauto and they're .92 each plus ship. New nuts, if you need 'em, as cheap as .62 each.

Anyway, there's a few options for ya, HTH & Merry Christmas!..............ed

p.s. No Worries about questions, that's the purpose of this forum!! 😺
See less See more

So I took Christmas and New Year's to mull over what to do next with the 3.4L.

Ultimately, I decided to let the shop handle more than originally planned.

However, I decided to skip on the first shop. They had really good prices but they seemed a bit run down and the reviews weren't great for that shop. I ended up taking my stuff to JMS Racing Engines in El Monte, CA. They had a nice shop, helpful staff and okay prices.

The cam and roller rockers arrived early from Compcams. I ordered cam bearings, freeze plugs, head bolts and a new water pump from DNJ.

The shop is going to take care of hot-tanking the entire block, installing new cam bearings and doing a full valve job. They are also going to inspect the bed/heads and cylinders. I asked about how much they skimmed off the head/bed if they did have to go that route. They said no more than 0.002". That said I don't have to start adding head spacers until 0.010"

I won't order new rings, gaskets and main/rod bearings until the shop does a proper inspection on everything. I will still be plasti-gauging the main/rod bearings upon install, though.

They are backed up on engine assembly so they'll only be doing the machining and I'll be piecing it all back together. So far, the bill for hot-tank, cam bearings, valve job and inspection is at $600.

Shop should be done in 2 weeks' time. We'll take it from there! I'm super excited to get this thing going.
See less See more
  • Like
Reactions: 1
Moving along smartly! Sounds like you found a simpatico shop, that's always a plus.
ALRIGHT so I finally got the block back from the shop. Cleaned, new cam bearings installed and they did a valve job.

I have all my parts ready. Bearings, seals, new cam shaft, new pistons ( I had a cracked piston ) and all seals.

I go to test fit the main bearings so I can test for clearances. The rear bearing does not go.

These are the bearings I have: 1995 Chevrolet Camaro 3.4L Main Bearing Set MB3114.E62

It's the only set of main bearings I can find for this motor but check out the rear bearing:

Vehicle Automotive tire Tire Bicycle part Motor vehicle

Do I have the wrong bearings?
See less See more
I have zero experience with this engine. But the bearing with the thrust surface is usually somewhere around the middle.
  • Like
Reactions: 1
Good On your shop, finding the busted piston! Bodes well for the remainder of the work.

That bearing shell with shoulders is the Thrust bearing. The 2 halves of that should go on the middle journal, which is #3 bearing. Note all bearing caps are marked 1,2,3, etc. The arrow on each cap should face forward and any bearing shell with a groove down the middle should be inserted in the block, not the cap.

Be sure you take a feeler gauge and check the clearance between the outer face of the thrust bearing and the block; I had a crank kit on an Opel 1900 come back with the thrust journal not machined to fit the oversized thrust bearing. When I bolted everything up the crank wouldn't move! Took me a while to figure that out.

Human body Jaw Organism Gesture Font
See less See more
Dangit you beat me to it! I was about to delete my last post in shame. I have a rebuild guide with me but it didn't have a photo of the bearing placement. I googled it and realized it was the thrust bearing. This was a d'oh moment. Anyway, I'll be measuring clearances tonight with plastigage and feelers.

Thanks again ed!
  • Like
Reactions: 1
So clearance specs are 0.0015 to 0.0025. All of em land around 0.002 except for the rear at closer to 0.0025 - 0.003. The crank surface at the rear showed a bit of light scoring, even after the shop had polished em. I can feel the scoring with my finger nail. Should I be concerned? Or am I splitting hairs?
Oh, I forgot, when you go to measure the thrust surface, tap the crank to the rear (or all the way to the front) with a soft mallet or cushion the crank with a chunk of wood and use a hammer if you don't have a mallet. If driven to the rear, the total thrust clearance will be measured at the front of the bearing shell (and vice-versa).

You'll note on the rear main, there's a small oil passage hole, and an O-ring is supposed to go there. I used a very sparing coating of Permatex 518 anaerobic sealer on the O-ring and on the machined surfaces of the block where the flat surfaces of the bearing shell seat against. This sealer only cures where it's squeezed. So if any should squeeze out into oil passages, it'll never cure and will wash away harmlessly. You should also seal the "split" of the forward main cap in the same manner (no O-ring up there, though).

Speaking of that and Opels, years ago on the same Kadett 1900 I did a crank job on, the P.O. had RTV'd the heck out of the oil pump. The engine had lost oil pressure and spun a bearing. When I tore it apart, Guess What was in the oil passages? A bunch of RTV Blue. Learned a valuable lesson working on that engine.
See less See more
  • Like
Reactions: 1
Thanks Ed! I'll keep an eye out for that O-ring passage. Not too sure which one it is or which O-ring to use but I'll cross that bridge in a few days. I'm going to take the crankshaft back to the machine shop to see if I need to grind it down. The scoring has me worried.
So clearance specs are 0.0015 to 0.0025. All of em land around 0.002 except for the rear at closer to 0.0025 - 0.003. The crank surface at the rear showed a bit of light scoring, even after the shop had polished em. I can feel the scoring with my finger nail. Should I be concerned? Or am I splitting hairs?
My V6 rebuilding book by Tom Currao says that a slightly-out-of-spec crankshaft that's never been turned, can be corrected by ordering (1) each .001" undersized bearing insert for that main. Just to be clear, that's .001" more undersized (i.e. a thicker bearing shell) than whatever bearing you're putting in now. I'm assuming you're installing new Standard bearings, since the shop only polished the crank, and didn't grind it.

If you use both .001" undersized bearing inserts, then it of course will reduce your total bearing clearance by .001". So if you're running .0025" to .003" now, you'd end up with a final clearance of .0015" to .002", right in spec.

Or, if it ends up a bit tight, you can use only one bearing shell, and that will reduce your total clearance by .0005" This would put it at the high end of the spec.

I would shoot for the low end, a bit tighter in-spec will give you better oil pressure. Too loose out-of-spec will reduce oil pressure, not desirable.

Far as the score goes, if it's just one line, don't forget that the bearing itself has a pretty good-sized groove going down the middle! The score will hold oil, so it should be OK. Now, if there was a bunch of scoring (i.e. "threading"), that'd be a Bad Thing.

So, that's what I'd do; either contact the machine shop and see if they can get that -.001" bearing insert set for (1) journal, or see if the GM dlr can do it. If you can't find it, I'd get the crank reground.

Just IMHO..............ed
See less See more
1 - 20 of 77 Posts