Advice on head options for 1HZ-T (1 Viewer)

[DamoPeru]

Hi all,

Sorry if i'm a bit long-winded here, but here's the background to my dilemma .

I've had continuous bad luck with my build and am now about to rebuild my 2002 1HZ (in HZJ78) for the third time.

The first time was a standard rebuild when i first bought it in a non-operative state. 20,000km later and a few km out of a workshop, the bottom cab heater hose 'mysteriously' blew off completely whilst on the highway on a test drive for my new gearbox, leading to an overheating disaster in the rear cylinder a few seconds later.

The second rebuild was on the premise that the head was tested as ok by the rebuilder. To make the best of the worst I added 1HZ-T pistons, gaskets etc. and a 1HD-T boost comp for the standard 10mm pump. Once fitted I added 3" SS straight through exhaust from turbo (AXT garret water/oil cooled), 2.5" PWR front mount air/air intercooler, increased turbo to 13psi, max tuned the pump to the point where compensator achieved max difference between min/max boost, dynotuned down to approx 180hp at the flywheel after getting around 200hp. I was happy as Larry until with less than 3000km on the clock another symptom apparent from day 1 came to a head, literally. While the motor ran perfectly, i was losing coolant from the overflow, initially dismissed as they lost my radiator cap during the rebuild and replaced with one lying around, but when the new cap arrived, and the same day seeing the problem in action when on the dyno (exhaust gas in the cooling system), it became apparent the gasket or the head was dodgy. To cut a long story short, the head is cracked, the rebuilders re-torqued the head bolts to 100Nm hoping it could be the gasket which made it worse (one cylinder stopped firing) and have now wiped their hands of any responsibility and I'm getting it pulled apart and rebuilt elsewhere.

Now to get closer to my question after that long introduction... Again to make the best of the worst I'll be ceramic coating the pistons, having the camshaft and new pistons balanced and I might remove that division on the intake manifold. My initial reaction was just to buy a brand new identical head from Toyota (11101-17050), but then I looked into the original 1HZ-T head (11101‑17030) but its discontinued as I expected, now replaced by another for European landcruisers and coasters up to 1999 (11101 - 17010), and i know other pre 97 (11101‑17011) and pre 99 (11101‑17012) heads exist for general market models as well like the 80, which some say were better (stronger).

So here is my question finally, in the interests of improving reliability for what will be a 3.8t world tourer, is it worth me looking into another head option from a pre 99 1HZ or even a 1HD-T while i have the chance? I know one bloke in Oz did the 1HZ-1HD-T hybrid thing but being here in Peru where all parts need to be imported I'm not sure if I'm so game to try that (due to time delays caused by needing that extra part that was overlooked in the last order), unless someone can give me the complete recipe. But the older head might be a goer if it can be done and there are real gains to be had... that's what i have no idea about, whether the changes in head post 99 where really just for 1. cost/weight/emissions cutting, 2. performance or 3. both, I suspect 1 or 3. all i have read on LCOOL is that most 1HZ turbo head problems arose sharply in the post 99 engines with the new head and pistons, but i don't know the details. if it resulted in no performance improvements l'll consider it.

So what would you do in my position? I'm in Peru so other motor options aren't an option.

Cheers,

 

[ForealBoreal]

To do a 1hz swap you will need (don't take my word as gospel please)

Head of course,
Injector lines
Injectors
Glow plugs

1) Cost/Weight/Emissions.
I would think better emissions from a DI engine but fractionally.
Cost wise those two stage injectors are expensive yet alone hard to find and have someone to deal with them.
Weight no difference.
I think the 1HZ is better suited for expedition use as it can handle running worse fuel in it in comparison to the 1hd-t. Parts are available everywhere let alone single stage injection can be set up by anyone at an injection shop. Dual stage will be a problem. 1HZ are all around the world.
You will get better fuel economy with a DI engine. The price in the end for savings in fuel its minimal over the long term. You will never pay conversion to 1hd-t with fuel savings....

2) Well if you have the upgraded pistons I wouldn't worry about them.
If I had them I would be getting a bigger g-turbo and putting 25-30psi into them...
Airbox and intake manifold will need to be done in my opinion along with a proper tune....

The Post 99 1hz is different in a few ways. Inectors spray pattern, angle and a few other things mainly for emissions sake.

I found a document a while back showing all the differences between the pre and post 1hz. I will try and track it down.
Honestly I would stick with the 1HZ instead of shelling out a ton of money for a questionable 1hd-t that may s*** the bed in 20,000kms.

 

[ForealBoreal]

here is the info on the pre and post stuff:

http://www.fuer.es/images/1HZ 1HD-T Engine.PDF

 

[Locked79]

Don't forget 1hd-t pistons as they have the combustion bowl built in

 

[DamoPeru]

here is the info on the pre and post stuff:

http://www.fuer.es/images/1HZ 1HD-T Engine.PDF

cheers, thanks heaps for that, some nice reading for tonight! yeah, while i'm not discounting it today, I'm pretty sure going HD is not a good option for me, leaning more towards either of the 1HZ ones for simplicity and reliability... but I have little time to decide and then its final. but yeah if this was just for local wheeling i'd go the HD-T head without thinking just for the fun of it, but in my case there's a lot at stake if it ain't solid.

 

[Dougal]

I'd suggest either a wideband O2 gauge or an EGT gauge to stop cracking your head again. The boost and power you were running suggest it was far too hot/rich and this cracked your head.

 

[ForealBoreal]

Dougal hit the nail on the head.
Those auber digital gauges are cheap and you could get one of the dual ones to monitor both parameters.
Get an Pre turbo EGT set up and set it to 1200F and you'll be more than golden.

 

[DamoPeru]

I wish I had of cracked the head having fun using it, but unfortunately it overheated when a cab heater hose blew off altogether on the highway just out of the workshop on the H151F transplant and new turbo test drive. Destroyed the rear cylinder. the head was then supposedly tested for cracks, the rebuilder told me it wasn't so we rebuilt it as a 1hz-t, and to cut a long story short it turns out I rebuilt it with a cracked head so it's back to the drawing board with less than 3000km on the clock, despite the fact I had it running perfectly tuned to 650C pre turbo. I actually already have four of the aubers: egt, psi, oil and coolant temp. I'm now hoping it will be a case of third time lucky with the motor rebuild and my streak of bad luck ends. Starting to lean towards DI though, just a matter of whether it's significantly more than what I'm already up for.

 

[Dougal]

How long is your EGT probe and was that 650C obtained with a foot flat to the floor for several minutes? Because a 1HZ producing 180hp on 13psi boost requires an A/F ratio around 15:1. Which will give an EGT far far higher than 650C.

I always understood an overheat would warp heads and cause head gasket leaks. But it takes combustion chamber overheat to crack the head.

 

[DamoPeru]

Hi dougal, any chance you want to fly out and help tune the beast once she's back together? You seem to know your stuff! 650 attained after a minute in 3rd to the floor @ 3000rpm. Probe has about 6-8 mm exposed I'm guessing but I will measure now its in bits. I have FMIC, 3" straight through exhaust from turbo and heat wrap on exhaust.

When I cooked it just after a long but easy hill, prior to any of this, she was stock 1HZ pistons and exhaust, no boost comp or IC, no EGT installed yet but the pump fuel screw had been adjusted up and it hadn't yet been tuned. On the previous drive, a year prior, the new turbo with fuel adjustment had blown the R151F in a matter of hours, mind you that box had been dropped 4 times since I took ownership. So whenever the hose blew off, she no doubt emptied herself in less then a minute but judging from where I ended up I'd say it coincided with me gasing up a hill at 110 in 5th with a fuel rich untuned pump and no sensors hooked up, so all combined cracking is a possibility. How many seconds do you reckon she'd last under normal conditions at 110 km/h with no coolant whatsoever?

 

[Dougal]

Hi dougal, any chance you want to fly out and help tune the beast once she's back together? You seem to know your stuff! 650 attained after a minute in 3rd to the floor @ 3000rpm. Probe has about 6-8 mm exposed I'm guessing but I will measure now its in bits. I have FMIC, 3" straight through exhaust from turbo and heat wrap on exhaust.

I'd love to, I've got an invite to a wedding in Argentina later in the year, but sadly have far too much happening to be able to make that trip.

Best EGT test is the highest gear and at ~2000rpm. Generally EGT isn't a problem at higher rpm as turbos are at full boost so airflow is higher and fuelling is tapering off.
Your probe needs to extend right to the centre of the pipe. 6-8mm means you're reading more of the pipe temperature and less of the gas temperature.

With a FMIC you'll be much better, I think around 17:1, but IMO it's still too rich for a 1HZ. If you bumped the boost to 15psi you could be safe to 400Nm peak torque and see what power figure you get on that tune.

When I cooked it just after a long but easy hill, prior to any of this, she was stock 1HZ pistons and exhaust, no boost comp or IC, no EGT installed yet but the pump fuel screw had been adjusted up and it hadn't yet been tuned. On the previous drive, a year prior, the new turbo with fuel adjustment had blown the R151F in a matter of hours, mind you that box had been dropped 4 times since I took ownership. So whenever the hose blew off, she no doubt emptied herself in less then a minute but judging from where I ended up I'd say it coincided with me gasing up a hill at 110 in 5th with a fuel rich untuned pump and no sensors hooked up, so all combined cracking is a possibility. How many seconds do you reckon she'd last under normal conditions at 110 km/h with no coolant whatsoever?

I'd hate to guess.

The last time I lost a hose (water pump bypass on a 4BD1T) I only noticed when I went through a creek and got clouds of steam. I was ~300km from home and it was snowing. I stopped about 6 times for more water on the way and the head survived fine. I love steel heads.

 

[DamoPeru]

Cheers, thanks for the info mate, I'll try that test as well next time. I had just been going off the Safari 1HZ turbo tuning guidelines.