1HZ exhaust valve clearances suspiciously tight - should I pull the head?

[DivByZero]

I'd like a second opinion and some advice. First, some background. I have a HZJ80, which has never had a turbo. The 1HZ engine has an aftermarket head, which was fitted new around 7 years ago and built by a reputable shop, after finding there were cracks in the original head from an earlier overheating event (occurred about 2 years prior, symptoms weren't obvious immediately). Injectors and pump were done around 5 years ago. Engine has 498,000kms as of today.

So I last did my valve clearances about 18 months ago. I didn't keep records, but I know a few of them were badly off. They hadn't been checked since the head was replaced, so without a baseline, I just brought them all back to spec and I've been driving it since then. About 10 months ago I moved from about 30m elevation to around 700m elevation. After this, I noticed an increase in black smoke under load, which isn't entirely unexpected given the elevation change, however I'm frequently driving from 700m to 900m up some fairly noticeable slopes, so this dirty exhaust condition has been happening quite a bit. The black smoke may have been getting worse, but it's hard to measure that kind of thing, and maybe I'm just more aware of it than I was originally. More concerning to me is that on the last oil change (about 5 months ago) I noticed the oil was much thicker than I've seen before, which, correct me if I'm wrong, is probably due to increased carbon from the dirty combustion I've been running.

So I've been poor on time (and, well, just poor in general), but this weekend I finally got new parts and time set aside to do the filters, timing belt, brakes, and a full tune-up. First thing I did was take some compression numbers (actually, took these last weekend):
1 - 440psi
2 - 445psi
3 - 455psi
4 - 458psi
5 - 468psi
6 - 449psi
These are from a hot engine. Specs say the range is 384-520psi with a max 70psi spread, so for an engine with half a million kms on it I think those are reasonable figures, although other opinions are welcomed. A full bottom-end rebuild is something I do plan to do with this engine eventually, but with those numbers, not something I'm looking at doing today. Next thing I did was change the air and fuel filters. I fitted some clear hose to the injector pump just to verify I'm not getting air in the lines, which I haven't had symptoms of, and it looked good, no bubbles. Oil filter/oil change is pending, because I wanted to check the valve clearances first.

So I removed the rocker cover and took clearance measurements on the valves. They're not so good. Clearances are as follows:

Cylinder	Intake	Exhaust
1	0.14mm	0.04mm
2	0.14mm	0.28mm
3	0.15mm	0.15mm
4	0.14mm	0.35mm
5	0.16mm	0.23mm
6	0.12mm	0.22mm

Factory specs say the range is 0.15mm - 0.25mm for intake, 0.35mm - 0.45mm for exhaust. The intake numbers show a mostly even nominal drop, and they're out of spec, but it's possible I did a dumb thing and set them to the minimum clearance values rather than shooting for the middle or upper. Can't recall. The exhaust clearances though.... assuming I didn't massively screw up when I did the last adjustment, the exhaust valve clearances, apart from cylinder 4, are all WAY off.

What I'm debating now is, do I try and bring them back to spec and button it closed, or should I be pulling the head? What worries me is that the valve shims I'd need to fit are WAY out of factory range. According to the FSM, shims in the range 2.35mm-3.30mm are available. I pulled exhaust shims 1 and 2 to measure (ran out of light for more), and they came up as 2.36mm for the both of them. At those values, I'd need shims that are 2.00mm and 2.24mm thickness, respectively. I don't have any that thin, nor do I think sourcing them would necessarily be the right move.

I'm wondering if I have burnt valves, or just otherwise gummed up exhaust valves which are caked with crap and not sealing tightly as a result. Does this sound likely/possible? I was planning to check the injectors to see if they were all healthy, or if they were contributing to the smoke problem (along with checking injector pump timing), but now I'm wondering if the black smoke is actually a result of exhaust valves not sealing properly. Wouldn't I have measured worse compression numbers if this was the case though?

I'd like some advice before I go nuclear and pull the head. Any thoughts guys?

 

[mudgudgeon]

The main reason valve clearances get tighter over time is valves receeding into the head due to worn valve seats, or worn valves.

Do you know the source for the aftermarket head? How is their reputation for quality

I had the head off my 1hd-t, and 1hz engines at around 200-250k km. Valves looked really good in both. No issues with achieving FSM clearances.

I don't think really thin shims is a good idea.

FWIW, my hzj105 was noticeably smokier in the mountains compared to around Sydney metro.
I first noticed in driving from Katoomba to Mt Vic and was worried something was wrong, but it was the same as usually back near sea level

 

[Gerry McGerry]

I first noticed in driving from Katoomba to Mt Vic and was worried something was wrong, but it was the same as usually back near sea level

Perfectly normal to feel dread passing through K-town, happens to us all.

Out of curiosity, was the HZJ turbo & would that make a difference? I've never noticed an increase in smoke crossing the mountains (1HZ turbo, 1HD-FT, TD42 turbo) but never had an NA diesel.

 

[mudgudgeon]

Perfectly normal to feel dread passing through K-town, happens to us all.

Out of curiosity, was the HZJ turbo & would that make a difference? I've never noticed an increase in smoke crossing the mountains (1HZ turbo, 1HD-FT, TD42 turbo) but never had an NA diesel.

Mine was not turbo'd at that point.

Turbo definitely makes difference. the turbo is forcing more air into the engine. At altitude, the air is less dense, so less oxygen available to burn fuel.
Turbo partly makes up for this.

 

[DivByZero]

Do you know the source for the aftermarket head? How is their reputation for quality

No unfortunately, I didn't pay as much attention to that at the time as I should have. I DO however have a complete genuine head sitting on my workbench, which I'd planned to rebuild and swap when I had the time, precisely because I wasn't sure whether I trusted the aftermarket head for the next decade. I'd have to go through the process of checking that head over and giving it some TLC though, I can't swap it in today. I'd planned to fully strip it down, get new valves, precombustion chambers, springs, seals, washers, and bearings, and get the head cleaned and machined by a shop. Not sure I can stretch to all that today, I'd hoped to do this a year from now.

FWIW, my hzj105 was noticeably smokier in the mountains compared to around Sydney metro.
I first noticed in driving from Katoomba to Mt Vic and was worried something was wrong, but it was the same as usually back near sea level

That's definitely been my experience, and I had noticed the smoke disappear as my altitude dropped back when going into Sydney. Since I'm going into Katoomba (1017m) several times a week though, and going to Wentworth falls almost daily (867m), while I live at Hazelbrook (700m) what I'm worried about is the effect on the engine health from running such dirty combustion on a daily basis. I'm seeing it in the oil for example. It's making me re-think a turbo, not for power, but with an extremely low boost to restore sea-level atmospheric pressure regardless of altitude.

 

[mudgudgeon]

what I'm worried about is the effect on the engine health from running such dirty combustion on a daily basis

a NA diesel is far more tolerant of a dirty tune than a turbo diesel.
If your coolant temp isn't being affected, I'd say don't worry about it too much
Cooking it and cracking the head is more of a concern than valves in the 1hz

 

[DivByZero]

So I... err... did a thing this weekend:

This isn't my engine. So a listing came up on FB marketplace. This is an 80 series 1HZ, out of a 1997 model with 376K on the odometer. Listed as suits rebuild with signs of a knock developing in the bottom end, but the entire thing cost me $1800 with all the bolt-ons, and it was only 40 minutes from my house. At that price it felt like a no-brainer, it gives me a ton of parts and plenty more options.

I was hoping for a genuine head but I can see it's aftermarket, but it has been done fairly recently from the look of it. Story is it was in a rig bought by someone with money. Builders were checking it over, recommended rebuilding the engine, he went out and bought an engine to swap instead. Mechanics thought bearings needed doing but it was running, not catastrophic. They haven't opened it though (visibly that's clearly true). Engine was in the vehicle running until a week ago. I saw the rig there it came out of with the new engine being put through some paces at the time. Seems legit. Engine was on a palette at the shop, they loaded it on a trailer and I parked it in my garage. Now working out my next steps.

So here's my thinking - I believe my 1HZ needs a rebuild. I buttoned it all back up and I've been watching it and thinking it through. So with the valve clearances so low with such small shims, it could only mean my valve seats or valves themselves are badly worn, probably both. The aftermarket head has probably worn worst and failed me here. It's not the only problem though. So my compression numbers in the driveway were OK, but what I see when out driving is a significant increase in smoke when under load. That doesn't just mean revving high, it means, I can be doing 2500 in 3rd on the flat, no smoke, then when I hit a slope, I get black smoke increasing. Logically, the only difference there is that the crank has more resistance to turning, so the pistons have more resistance to going down on detonation. That should make no difference to emissions, if the combustion chamber was keeping pressure. The only conclusion I can draw, is that I'm getting blow-by which is manifesting under load, but doesn't show up when the engine is sitting happy at idle in my driveway, which seems reasonable. This would also explain my thickening engine oil. Symptoms are worse when the engine is cold, reduce once it's nice and warm, but never go away. I think the shift to higher altitudes has made it harder for me to diagnose because it does produce more smoke at this level, but what I'm seeing isn't normal, and appears to me to be getting worse. At half a million kms though, I think it's done alright, especially given how I drive it, and my often poor oil change schedule.

I've been in a situation like this before with an LN106 Hilux, and I don't want to repeat the mistakes I made there. I want to keep the vehicle on the road while I work on the engine, otherwise it'll end up as another project car that sits for the next 5-10 years. My current engine is running, but tired. I have this "new to me" engine, which is running, probably has a good top end, but the bottom end needs work. A better option might have been to spend $5-6k on a running engine I could inspect and see running, and swap that in, but I couldn't afford that route. I'm happy with the $1800 option I found, even if it means a bit more messing around.

I'm strongly considering doing a double-engine rebuild. First, I'd open up the donor engine. Goal would be to do the piston rings, and crank/conrod bearings, and absolutely nothing else that doesn't need doing. I'd inspect the crank, stick the micrometer on it, look for cracks, and if it looks good to me, or good enough at least, shove it back together with existing pistons, rods, everything else, and swap the engine into my car as a temporary, runnable engine. I would then have my original 500km engine on a stand, and time to do a rebuild on that carefully, slowly. I'd fully strip it down, get the block decked and honed, paint it up, new pistons, the works. As for the head, I may even drop the $2k and get a brand new factory head, and drop in brand new valves, while reusing the camshaft. After all that, I'd have a new engine ready to take me to 1,000,000km.

Now the work doesn't scare me. I don't see engine rebuilds as being that difficult TBH. The machining work I'd pay for. The assembly is straightforward if you're methodical and careful, and there's lots of good resources out there to help (IE, this video set is great - ). The money scares me. I'm not flush with cash, and every purchase will need to be budgeted for. If I'm going all genuine for my proper engine rebuild, I know how expensive this gets, but if I'm doing it over time, which I have to since I'm doing all the work and need to fit it around life, I can work the costs in.

That's my current thoughts anyway. It makes sense to me, when I consider that my plans are to own and drive this 80 series for the rest of my natural life. I do see myself owning it in 30 years time, so this is a once in 30 year investment.

I'm very interested in any thoughts, opinions, words of advice, encouragement, caution, anything. Very much still weighing up my options, and not trying to rush into anything.

 

[mudgudgeon]

I'm strongly considering doing a double-engine rebuild

Been there . . .

Still haven't touched on the 2nd rebuild.


Temporary solutions that are good enough to last indefinitely often stay permanent.

If it's good enough to work indefinitely, why not do it good enough to be permanent?

If money is the reason, a poor man pays twice. ( been there too! No judgement)

By the time you strip down the used engine, replace bearings, seals, rings, head bolts, all the other little odds and ends you find, you could be nearly $2k deep into the shopping cart.
That's 3-4k to buy some time. That puts you 3-4k further away from rebuilding yours.
All this is hinged on the condition of the used engine's bottom end.

You could have that engine torn down in a weekend, doing an initial inspection as you tear stuff down might change your options.

Another option is do a full and thorough rebuild on the used engine with the intention it becomes the permanent solution.
Drive yours until it fails, or you have the other one ready.

Do a leak down test to see if you are getting blow by.
Get an oil sample analysed to see if you have bearing wear happening.
These two things will give some indication if you're facing an imminent failure.
Could a bit of heavy soot from the 1hz be lived with? (maybe not for the person behind you!)
Make sure your insurer covers towing in the event of a breakdown. Or take out RoadSide assistance cover with NRMA, ALLIANZ ETC.

 

[DivByZero]

I've been weighing my options this week, and I think I'm clear on my next steps at least. Next step is to do a minimal dive into the donor engine and see what's what. It reportedly had a sus bottom end. The top end however looks quite spiffy and relatively new. The aftermarket head has ARP head studs on it. Those are not cheap, and suggest it was done with some money behind it. Significantly for me, ARP studs are not TTY and are reusable. It has a three notch head gasket fitted, and I happen to have a three notch head gasket on my parts shelf already, and I have a timing belt on hand too, although I'll probably reuse the current one if I think it looks serviceable. That means I can pull and re-fit the head with no cash down today.

As for the bottom end, it really depends what I find when I pull the pan. If it's full of shrapnel, I'll take a beat and consider my next steps. If not, I pull the crank and pistons, and measure/inspect everything. If it looks like I can get away without machining (and I'll take my time on making that call), piston rings plus crank/conrod bearings and thrust washers come to about $600 through terrain tamer. It's only a couple of misc gaskets, some assembly lube and a bunch of threebond after that to put it back together. I'd leave on absolutely everything else. Apart from that it's just my time, oil/coolant, and an ac regas, since I don't have the pump to reclaim/regass that myself. Not too bad I think. If it works out this way. I'll know more when I pull the pan.

I understand the logic in an oil analysis and proper leakdown test. I've got a leakdown test kit on the way. I may end up doing oil analysis, but it's not something I'm arranging right away, and to be honest, I'm not sure the results would change my course of action much. If it says the engine isn't healthy, it needs a rebuild, and I'd rebuild the original engine properly, over time, doing everything. If it says the engine is healthy, well I still need to pull and rebuild the head (probably with a new head itself) on the data I already have anyway, and if I'm doing that, I'm inclined to do the bottom end too and have a fully refreshed engine. Either way, the original engine is due some major surgery.

At any rate, first I'm going to take a look at the engine in the garage, and go from there. If the bottom end is cactus, I might consider the middle road option, swapping the new head onto my engine. If I end up there, that's where the oil analysis could come in handy, to tell me if that's an option, or I really need to pull the whole block. Even if the bottom end looks good on the original engine, and I don't have a good temp engine to use, I might go for dropping the pan, and pulling and re-ringing the pistons without pulling the crank or removing the block. I could do that in short order if I already had the head cleaned up and on a bench ready to go.

Anyway, I'll see how it goes this weekend.

 

[DivByZero]

Well, today couldn't have gone better. The donor engine with the suspect bottom end isn't apart yet... because I don't think there's a damn thing wrong with it. The first thing I went to do on it after mounting on the engine stand was remove the harmonic balancer. It came off fairly easily with a few ugga duggas... or at least part of it did:

So the harmonic balancer is two metal parts glued together by vulcanised rubber. When the rubber fails, the balancer separates and the outer part starts grinding away at the front of the engine like you can see in the image above. I've written before about how these balancers after 30 years are now all timebombs waiting to go off:

Harmonic balancer fail?

Pretty sure it’s finally let go and the mis-alignment of my belts is because of it. Unless you think the crank bolt decided to walk itself out. Have a look at the amount of rubber showing on the back side of the crank pulley. It kept sleeping the alternator belts and I couldn’t figure out why...

forum.ih8mud.com

This one had totally failed, and was grinding on the timing gear cover, a noise I'm familiar with from when mine separated, and definitely sounds like something catastrophic has happened in the bottom end. It appears the owner went out and got another engine without much further investigation.

I drained the oil - no ferrous metals from dragging a magnet through it. Ran half the oil through a filtering medium - no visible contaminants or bearing materials. Tore open the oil filter - no visible metals or other contaminants. Turning the engine over by hand from the crank bolt, it feels nice and smooth.

So this is a case where I definitely am going to send away for oil analysis. Since I haven't been able to see/hear it running, and I'm not setup to safely run an engine out of the vehicle, this will help me have more confidence in it before I swap it into the vehicle. I started later than I planned today, so i didn't get the rocker cover open to check valve clearances, but I'll probably do that in the next couple of days. Right now though, for $1800 with all the bolt-ons, it looks like I might have won the used engine lottery. A new harmonic balancer, new oil filter, and a replacement for the leaking rear mail oil seal, and right now I'm betting this'll be a perfectly serviceable engine.

 

[mudgudgeon]

I'm not setup to safely run an engine out of the vehicle

If you really want to here it running, tou could get a used, wide tyre.
Plonk the engine down in the middle of it, and start it sitting cradled in the tire with a couple of straps, one each side to strap the engine to the tire so it can't tip over.
You only need a fuel container with a pickup and return hose, power & ground for the starter, power for starter solenoid, and fuel shut off solenoid.
You do need a bellhousing and flywheel to mount the starter. This contains/protects the flywheel.

I've run several engines like this over the years.
Just don't rev it to aggressively. Shut down will see the most movement due to inertia

 

[DivByZero]

Got the oil analysis back on the donor engine today:

Looking pretty good to my eye, although I'd love to hear feedback from anyone who's used these services. The 20ppm aluminium level was flagged, but 20ppm is also the minimum level at which they flag it an issue, and at 19ppm it wouldn't be mentioned. Could be indicative of a level of bearing or piston wear, but nothing you'd tear down the engine for. They flagged a likely internal coolant leak. I'm not certain of that, as the coolant contamination flagged could have actually come from the funnel or container I used when draining/transferring the oil, as I didn't make sure that was perfectly clean. Even so, if there is a leak there it's minor on those numbers, which means I won't lose too much sleep about running it for a temporary donor. I could always pull the head later if there was a concern, but I do suspect contamination on transfer was a factor.

Now I haven't done an oil analysis on my current engine, because I'd just drained it all and poured it into a mixed bucket of used oil for disposal before checking the shims, which I thought was going to go better than it did, and I haven't put enough hours on the engine since then for the oil results to be very useful. I may drive it a bit more over the next month, gently, keeping an eye on it, just to get a usable oil sample to send in for analysis too. I think that would be very worthwhile before I rip it out of the vehicle. I may also attempt to start the donor engine as per your suggestion @mudgudgeon. I have a spare bellhousing, starter (freshly rebuilt even), flywheel, and tyres/pallets/ratchets I could use to rig something up. I have a couple of spare primer pumps too, so I could protect against contamination getting into the pump/injectors easily enough. That's probably something I'll have a crack at doing sometime in the next month or so. I'll need to get a new harmonic balancer first though, don't have a spare of that on the shelf.

 

[mudgudgeon]

They flagged a likely internal coolant leak

I'd probably put it in and run it. Keep a close eye on coolant temperatures, if you haven't already, install an engine watchdog or auxilary coolant temp gauge.
coolant level, coolant contamination etc.
You could do an exhaust gas test on the coolant system.
And do another oil analysis at next oil change cycle when you know the status of the oil, filter, oil change interval, oil type etc

 

[DivByZero]

I'd probably put it in and run it. Keep a close eye on coolant temperatures, if you haven't already, install an engine watchdog or auxilary coolant temp gauge.
coolant level, coolant contamination etc.
You could do an exhaust gas test on the coolant system.
And do another oil analysis at next oil change cycle when you know the status of the oil, filter, oil change interval, oil type etc

Yep, that was my thoughts too. I have an oil pressure gauge plus pressure switch with dash light AND alarm, and a head temp probe on the thermostat housing with a digital readout AND alarm, so I'm well covered for anything that could go wrong with the oil/cooling systems. I'll probably start the engine out of the vehicle as you suggested for extra peace of mind (and hell, just for the experience), but I'm feeling really good about just dropping this engine in and running it. I'm going to run my current engine for a little bit and get an oil analysis done on it too before I pull it, no rush at this stage. I want to get the engine swap done before the rego check in late November, but I've got plenty of runway there still.