12H-T: to rebuild or not? (1 Viewer)

[Fifty Hertz]

Hi guys,

So I've been having some thoughts about the extent of potential engine rebuild given the current state of my project. Have a look here My HJ61 Rejuvenation

I got into some discussion on the Oz 60 Series Owners FB page and the opinions included pull the pistons and check, do pistons/rings/bearings regardless - all the way through to do a full rebuild.

Background. Before I started the project it was making a bit of the ole white smoke. I was intending to do a valve stem seal replacement with the head on and an injector pump service/adjustment. Now I've taken the head off for a rebuild due to the head gasket failure and it's getting new guides and seals anyway, along with a valve/seat recut and reface. It's also possible that the rings are passing a little but I'm not sure how much. I've never checked the compression figures. The white smoke was worse on cold start but still made some when hot. The oil consumption between services has always been undetectable. There has never been evidence of the coolant and oil mixing.

Now the head is off, should I do anything further? The car has an indicated 250,000 km and there's nothing to suggest that's not genuine. The engine always starts first twist, has no evil mechanical noises or knocks and in general shows no evidence of any serious internal problems.

What to do? My research suggests that 250,000 km is only moderate for a well maintained 12H-T and that it's more the peripheral things that may need attention at this stage - like the injectors, governor, head, turbo etc. All these things have been or are currently being addressed already. Despite some opinions to the contrary, my evolving view is to follow the age-old maxim "if it ain't broke, don't fix it."

As an engineer I generally like some solid evidence of a problem before throwing money at solutions that may not be required. I'm not going to throw between 5-10k at a full rebuild just for the sake of it. So I'm leaning towards just doing the minimum, i.e. check the block for flatness, inspect the bores (at first glance they look pretty nice) and refit the head if it looks ok. Once it's going again, I'll do regular compression checks and possibly oil sampling to determine when something needs doing. If it does need it while I still have the 60, I would probably then do a full engine rebuild rather than selected bits as has been suggested. To my mind it's better to do it once and properly.

I'm interested to know people's thoughts.

 

[VX 12HT]

look normally i would have said don't bother its relatively low kms for a 12ht but i would look at the pistons and put the upgraded alfin piston inserts in seeing as you have it apart. White smoke unburt fuel so injector checking time had mine done united fuel injection not the cheapest but great job had them cleaned and flowed tested. Did you say you had a g turbo going on if so another reason for the piston check and compression and these put a lot of pressure on an older motor . My one only has a 185,000kms on and like yours uses no oil but if going the gtutbo way i would check it for long time reliability. Shaun from 4wd Action mag did not have good experience with g turbo on his older motor.

 

[Fifty Hertz]

I hear ya on the piston replacement. Only thing is I don't really have it apart, it's just the head off at this stage. Swapping the pistons would be great, but since the only decent ones readily available are oversize, it would need boring. That's an engine out and total tear-down job. And if you're doing that, you might as well do everything.

Hmmmmmm, pondering the options...

 

[VX 12HT]

yeh as you said if she is hardly using any oil and compression is good it is still got a lot of life left in her.....

 

[Fifty Hertz]

I kinda feel like rebuilding is an all or nothing scenario. Looking at it now I know it's a rabbit hole that I'll go all the way down and just do everything "while it's apart". I keep coming back to the fact that so far there is no actual evidence of the need to do anything other than change the head gasket and fettle the fuel system a bit.

The engines on these are easy enough to pull, I'd do it easily in a day, with some help... now that I'm so intimate with it lol. If I put it back together and it runs sweetly like it was but the compression figures are below average, it's not the end of the earth. It's not going to fail immediately and catastrophically. I can monitor it and do it in 6 or 12 months time - when it actually needs doing.

I have a tendency to go overboard with my projects and gold-plate things for no real reason other than to feel good about it. I'm really trying to contain the scope on a project for once and only do what's really necessary. That's why I've resisted (despite the urge... which has been strong...) to lift the body and strip and paint the chassis and underside of the tub and the driveline components. It's lasted for 29 years with the factory paint and shows only a little minor surface rust in a very few places. I'll squirt a bucket of Fisholene or Tectyl or whatever over everything and that will preseve it just fine. I just won't be sliding a big mirror underneath for people to admire it at a concours.

Hell the engine in this thing may well see out the end of the age of fossil fuels before it actually needs a rebuild

 

[hj 60]

There is so much other maintenance to keep it driving fine, I focus on that with the government road check and some preventive maintenance.
And no money saving on safety (tie rods/steering, brake system) and trying to replace stuff that might stop it on the highway (belts, charging, drive axle)
The odo might be rolled back so any smoke and tolerances are the only advisor, get lazy and stop the gold plating.
Oke, fine, for peace of mind get the alfin inserts take time to measure tolerances as in FSM
alfin PDF wow what a long link



I bought this good 250k kilometer pistons for 10 euro (replaced "while in there"), might use them:

this is for my hj but they have 61 also:
Pistons Toyota Landcruiser HJ60 Category Search - Precision International

 

[Gengis]

Bores look sweet, i say new HG (really) and run with it. Spend the bucks on the road worthy stuff and save for a rebuild into the future.
By the way, any new on whether multi layer metal gasket is available for the 12HT ??

 

[Prairie Swamp]

As mentioned white smoke is unburnt fuel due to not enough heat in the cylinder, very poor spray pattern or bad timing. In any event also as mentioned your bores look good so the problem is likely valves, maybe HG, injectors or timing. The only real problem with white smoke is cold starting and I don't think it gets really cold there.

I'd put the head back on, maybe go through the injectors and check the timing. Without having to worry about -15C starts I would run it that way as long as it will go.

 

[roma042987]

check my 87 fix up thread in my signature. I went down the rabbit hole as you speak. First time around I only did the basics and it cost me. I would at least pull the pistons to check the condition of the ring lands. nothing but an oil pan reseal involved in that. if the ring lands are beat to hell you have your answer about the next step. if ring lands are good and rod bearings are good then you're at a crossroads...you could certainly stuff the factory pistons back in at that point if you wish.

Another thing to consider is a rebuild is MUCH cheaper on an engine that's in decent health as opposed to one that needs the crank turned. If you do a rebuild at this point you could do .5 over pistons and stock sized bearings. the only machine labor youd be out would be a bore, cleaning the block, and would be a good call to polish the crank.

 

[Fifty Hertz]

check my 87 fix up thread in my signature. I went down the rabbit hole as you speak. First time around I only did the basics and it cost me. I would at least pull the pistons to check the condition of the ring lands. nothing but an oil pan reseal involved in that. if the ring lands are beat to hell you have your answer about the next step. if ring lands are good and rod bearings are good then you're at a crossroads...you could certainly stuff the factory pistons back in at that point if you wish.

Another thing to consider is a rebuild is MUCH cheaper on an engine that's in decent health as opposed to one that needs the crank turned. If you do a rebuild at this point you could do .5 over pistons and stock sized bearings. the only machine labor youd be out would be a bore, cleaning the block, and would be a good call to polish the crank.

View attachment 1494373 View attachment 1494374 View attachment 1494375 View attachment 1494376

Wow that's a very pretty 12H-T. What paint have you used for all the engine components? Did you get a bunch of stuff zinc plated and gold passivated or did you buy new hardware?

I'd love to have my engine look like that, but paint and polishing isn't that important for longevity and usability. I'll get sucked up in making things look nice and gold-plating this project... which I'm strenuously trying to avoid. I really need not to look at such engine porn!

You have some good points. There's no real expense in pulling the pistons for inspection. Shouldn't one also replace big end cap bolts though if they're being undone? Like head bolts they should probably only be torqued once. Not sure with this engine if they're replaceable or integral the conrod? But yes if the pistons, rings and big ends look ok, it is a bit of a crossroads. And I take your point about a simpler and less costly rebuild on an engine that is still in pretty good condition.

 

[Fifty Hertz]

There is so much other maintenance to keep it driving fine, I focus on that with the government road check and some preventive maintenance.
And no money saving on safety (tie rods/steering, brake system) and trying to replace stuff that might stop it on the highway (belts, charging, drive axle)
The odo might be rolled back so any smoke and tolerances are the only advisor, get lazy and stop the gold plating.
Oke, fine, for peace of mind get the alfin inserts take time to measure tolerances as in FSM
alfin PDF wow what a long link



I bought this good 250k kilometer pistons for 10 euro (replaced "while in there"), might use them:

this is for my hj but they have 61 also:
Pistons Toyota Landcruiser HJ60 Category Search - Precision International

Ah right it seems that Precision have STD piston for the 12H-T. Would be a good option if the bores are as clean and unworn as they look initially.

 

[Fifty Hertz]

Bores look sweet, i say new HG (really) and run with it. Spend the bucks on the road worthy stuff and save for a rebuild into the future.
By the way, any new on whether multi layer metal gasket is available for the 12HT ??

I'm not sure what gasket I'm getting. I left that with my head builder and he is getting a complete head set for me. I queried and he said it would be a good quality set. I'll need to wait til I'm back in Australia in 2 weeks time...
Edit: Just checked my email. He's supplying a "Durapro" gasket set. General consensus on the interwebs is that they are good.

 

[roma042987]

no need to replace the connecting rod bolts. I've been powder coating my parts. The head and block are painted and the rest I powdered. Zinc plated all the bolts and injection lines and then clear powdered the lines too.

 

[Fifty Hertz]

no need to replace the connecting rod bolts. I've been powder coating my parts. The head and block are painted and the rest I powdered. Zinc plated all the bolts and injection lines and then clear powdered the lines too.

I admire your attention to detail. But I'm still going to pretend that I didn't see it

 

[Silveredition]

Replace pistons with Alfin re-inforced pistons while the engine is in situ, use a MLS head gasket, get the head reconditioned, bolt it back together, then start to enjoy the g-turbo'd 12HT....
(I will hopefully be doing the same one day - for now it is the standard turbo at 10psi....)
Ps - the above was recommended to me by Graeme @ Gturbo when I queried buying a grunter extreme for mine....

 

[Fred12HT]

check my 87 fix up thread in my signature. I went down the rabbit hole as you speak. First time around I only did the basics and it cost me. I would at least pull the pistons to check the condition of the ring lands. nothing but an oil pan reseal involved in that. if the ring lands are beat to hell you have your answer about the next step. if ring lands are good and rod bearings are good then you're at a crossroads...you could certainly stuff the factory pistons back in at that point if you wish.

Another thing to consider is a rebuild is MUCH cheaper on an engine that's in decent health as opposed to one that needs the crank turned. If you do a rebuild at this point you could do .5 over pistons and stock sized bearings. the only machine labor youd be out would be a bore, cleaning the block, and would be a good call to polish the crank.

View attachment 1494373 View attachment 1494374 View attachment 1494375 View attachment 1494376

 

[Fred12HT]

Replace pistons with Alfin re-inforced pistons while the engine is in situ, use a MLS head gasket, get the head reconditioned, bolt it back together, then start to enjoy the g-turbo'd 12HT....
(I will hopefully be doing the same one day - for now it is the standard turbo at 10psi....)
Ps - the above was recommended to me by Graeme @ Gturbo when I queried buying a grunter extreme for mine....

Good to hear, I spoke to Cuan at GTurbo last week and by the end of the phone call i'd bought a Grunter and PDI intercooler, though I was mostly committed prior anyway, no sales pressure tactics and both are on their way. I've just received my compression test results (currently getting the injectors serviced) and 1=380, 2=360, 3=360, 4=390, 5=380, 6=400 Im happy with these results but a little niggle in the back of my mind is not knowing the condition of the pistons, rings or bores and ideally having Alfin inserts before giving it too much boost. Any thoughts?
I'ver been running the stock Turbo at 15psi with more fuel for the past 20k and all seems well and I wont be going nuts with the GTurbo, maybe factory 18psi.

Am I right in thinking a garage tear down just of the head, to inspect the bores, top rings, and have the head serviced for valves etc and replacing gasket and bearings is a sensible step without going deeper?

Thanks for any advice!

 

[Silveredition]

Good to hear, I spoke to Cuan at GTurbo last week and by the end of the phone call i'd bought a Grunter and PDI intercooler, though I was mostly committed prior anyway, no sales pressure tactics and both are on their way. I've just received my compression test results (currently getting the injectors serviced) and 1=380, 2=360, 3=360, 4=390, 5=380, 6=400 Im happy with these results but a little niggle in the back of my mind is not knowing the condition of the pistons, rings or bores and ideally having Alfin inserts before giving it too much boost. Any thoughts?
I'ver been running the stock Turbo at 15psi with more fuel for the past 20k and all seems well and I wont be going nuts with the GTurbo, maybe factory 18psi.

Am I right in thinking a garage tear down just of the head, to inspect the bores, top rings, and have the head serviced for valves etc and replacing gasket and bearings is a sensible step without going deeper?

Thanks for any advice!

Well, I ended up going all the way…
Full engine rebuild / Gturbo (now set to 22psi), PDI Front Mount, +30% injectors, ADS modified injector pump, new H55, etc…
Upon tear-down, the engine was in a terrible state ;even though it produced good power, blew very little smoke, started instantly when the key was touched… it was using a bit of oil when towing though.
From my experience, I don’t think you know what you have until it is stripped and clearances are measured..

 

[Fred12HT]

Well, I ended up going all the way…
Full engine rebuild / Gturbo (now set to 22psi), PDI Front Mount, +30% injectors, ADS modified injector pump, new H55, etc…
Upon tear-down, the engine was in a terrible state ;even though it produced good power, blew very little smoke, started instantly when the key was touched… it was using a bit of oil when towing though.
From my experience, I don’t think you know what you have until it is stripped and clearances are measured..

Yes very true regarding the tear down, a bunch of indicators or obvious signs are good, but mostly only solid evidence is stripping and replacing for sure. Excuse my lack of knowledge, what's the ADS modified pump and H55?
As it sounds it was running well (apart from oil use, which mine seems to use very little, though haven't done any heavy towing) why did you decide to strip, just future proofing before power gains???

Looks like a tidy rig with the raptor coat and especially the blacked out fascia, i'm thinking about doing the same when I whip mine off.

Did you notice much lag with the GTurbo and intercooler combo? And do you think the upgraded injectors are needed to keep up with them both?

Cheers

 

[Silveredition]

Yes very true regarding the tear down, a bunch of indicators or obvious signs are good, but mostly only solid evidence is stripping and replacing for sure. Excuse my lack of knowledge, what's the ADS modified pump and H55?
As it sounds it was running well (apart from oil use, which mine seems to use very little, though haven't done any heavy towing) why did you decide to strip, just future proofing before power gains???

Looks like a tidy rig with the raptor coat and especially the blacked out fascia, i'm thinking about doing the same when I whip mine off.

Did you notice much lag with the GTurbo and intercooler combo? And do you think the upgraded injectors are needed to keep up with them both?

Cheers

Gday mate,
The H55f is the 5 speed manual gearbox (unless I got the model number wrong..!)
Yep, my engine was running great, but as I use it to tow my boat (max of about 1.2t on the trailer, fully loaded) on a 3000km round trip a couple of times per year with my wife and 2 young daughters, I wanted to ensure we weren’t going to have a major failure in the middle of nowhere (hence the gearbox replacement too…)
The ADS modified pump is a modification to the injector pump by an Australian company (ADS Injection) to suit the bigger injectors - allowing more fuel delivery, and including (I believe) 11.5mm plungers within the pump.
The lag is a funny one… once the revs get up a bit, the power comes on like an old 2-stroke motocross bike! But… the power is more throughout the range, so it may be exaggerated. It certainly isn’t unpleasant!
As far as the modified pump and injectors go, I am unsure if they, or one or the other is necessary, but I wanted the whole thing to work well from the start without having to go back and change things… I have heard there is a big difference just with the bigger injectors.
I had the 60 dyno tuned a few days back.
168hp (at about 2700rpm) and 539Nm (at 1900rpm) with AFR’s of 25:1 and a boost pressure of 22psi. I am sure I can get 200hp and over 600Nm, but I want longevity and cool towing temps. I am very happy with the results and more so, the feel of driving the car…