Advice on 1HDT engine

[Bueff]

good evening everyone,

I would like to get your opinions on a 1HDT that currently bolted in my 75 series, which is serving as a garden ornament at this stage due to gear box issues and old age and all the other thing that make it a project rather than a reliable vehicle.

The 1Hdt came out of a written off 80 series with rear end damage and has currently about 420.000 is on it, which is pretty normal for its age and being in Australia.

The compression test showed 420psi +- a few psi through out the motor. It runs smooth and blows a bit of black smoke. But I put that down to the previous owner who had a intercooler installed and most likely wound the fuel screw up a bit further.

Now to the important question, I am toying with the idea of swapping the 1HDT with the 1HZ in my Troopy.
What is your opinion on the fact that the compression test shows 420 and given the age of the engine. I understand it's always a bit of a gamble but I figure a factory turbo is better in the long run than a aftermarket turbo.
The turbo on the 1HZ runs about 9 psi and EGT's have never gone past 450 degrees.
When I bought the vehicle, the odd reading was 190.000 Tulsi I have since come to the conclusion that the sneaky bugger at the car yard changed the cluster unit. As everything in the dash is covered in red dirt, the cluster is rather clean.
My point being, I don't know the true k's on the motor.

So any opinions on the 1HDT, good or bad are most welcome. Anything I should be aware of and so on.

Much appreciated and have a good evening.

Jens

 

[Michael Montgomery]

Hi, Bueff welcome to the forum, firstly it's important to separate the engine to the gearbox. If the vehicle is not running right then we need to identify what issues it has to better effectively find a basis of understanding before making rash decisions.

The 1HDT engine is a good engine when all is in order and better more powerful than the 1HZ.

Black smoke is normal at startup bit not much after. Would check fueling on the pump first, injectors second and then adjust idle if need be.

Turbos even a Chinese branded one are not bad to have on there and don't determine the engines running and driving.

As for gearbox whats the issues?

Are the gears working right?
Is the gearbox biting the gear for taking off?
Whats the oil like?
And are there any noises whilst shifting otherwise should be smooth as butter?

If you have a friend or someone else with some experience be good to see there's if possible and compare.

 

[Trevor]

The 1HDT engine should be producing 498 psi per cylinder, but how quickly it reaches pressure is important too.

I feel your compression readings are on the low side, if it's taking more than 3 or 4 cranks to reach those pressures and given the black smoke I would have to initially suspect worn rings and/or leaking valves.

I appreciate there's no substitute for actually being next to the engine and fault finding via the forum is always tricky but these are my thoughts based on your info.

 

[Bueff]

Thank you for your information so far,

The gearbox has a rattle, that's the best way to describe it. If sitting at idle in neutral you can hear it quietly, when putting it in gear and taking off, it almost sounds like there are teeth grinding in all gears except 4th. It runs pretty smooth in 4th. I spoke to a mechanic and he thinks there is a bearing issue as the 4th gear apparently goes straight through. Any how, money and time are the biggest challenge to get this looked at.

There is also the old known issue of the oil draining into the transfer case, leaving the oil in the box low.

The 1HDT almost blows no smoke on starting up, only if you put your foot flat on the loud pedal it gives a short burst of black. I have just met a retired diesel mechanic in the neighbourhood, I might stalk him and see what he thinks if the black smoke. As soon as I take it to a shop, I am in for complete rebuild, I fear

I am not sure how many cranks it took to get to the reading as I personally haven't purchased a compression test kit so I left it to a mechanic I can trust.

Thanks again and please lkeep your opinions coming.

 

[Michael Montgomery]

Having rebuilt my 1HDT engine and fixed my gearbox issues as of last year kinda gathered some experience along the way. Your fuel pump may need a rebuild. Pretty common if the high mileage is a factor.

Denso specialist states after 250,000Km wear and tear starts. Mine probably was over 700,000 km easily. Had vibrations in mid-range gearing and performance issues with black smoke on driving hard and uphills. Now resolved as like-new thankfully.

As for the gearbox is your an A442F auto?

 

[Bueff]

Hi Dervis,

that makes sense in regards to the fuel pump,

the gear box is the stock standard 5 speed manual, its a 93 HZJ75. I don’t know the box description, but I doubt they made a auto for a ute back then.

thanks Jens

 

[chapel gate]

Thank you for your information so far,

The gearbox has a rattle, that's the best way to describe it. If sitting at idle in neutral you can hear it quietly, when putting it in gear and taking off, it almost sounds like there are teeth grinding in all gears except 4th. It runs pretty smooth in 4th. I spoke to a mechanic and he thinks there is a bearing issue as the 4th gear apparently goes straight through. Any how, money and time are the biggest challenge to get this looked at.

There is also the old known issue of the oil draining into the transfer case, leaving the oil in the box low.

The 1HDT almost blows no smoke on starting up, only if you put your foot flat on the loud pedal it gives a short burst of black. I have just met a retired diesel mechanic in the neighbourhood, I might stalk him and see what he thinks if the black smoke. As soon as I take it to a shop, I am in for complete rebuild, I fear

I am not sure how many cranks it took to get to the reading as I personally haven't purchased a compression test kit so I left it to a mechanic I can trust.

Thanks again and please lkeep your opinions coming.

The black smoke under the conditions you describe is perfectly normal.

Nothing wrong with 420 psi across the range. The fact that it's consistent is a good thing. I'm guessing with the compression figures, you have around 200000/250000 miles on the engine.

 

[Bueff]

The black smoke under the conditions you describe is perfectly normal.

Nothing wrong with 420 psi across the range. The fact that it's consistent is a good thing. I'm guessing with the compression figures, you have around 200000/250000 miles on the engine.

Yes indeed, it has done about 420.000 km, what ever the equivalent in miles is.

I sort of thought that consistency in the pressure is a good thing. But my mechanical knowledge is very basic at this point. But that’s about to change I hope .

 

[Bueff]

Alright, I finally managed to corner the friendly neighbor and quiz him about my engine. As a retired diesel mechanic, he wasn't too worried about the compression figures. He said the same as chapel gate, since the compression is fairly even through out the engine, it should be fine.

Which brings me to the next question, if I fit the 1hdt in my Troopy, would a box from a hdj78 fit the engine? I would prefer a box build for a factory turbo rather than a rebuild and upgraded 1hz box.

Also is the exhaust on a 75 the same or close to similar to the 78. I have a 3" on the 1hdt which is practically new. I am hoping to transfer that one over too.

Many thank and have a good evening.

 

[Iwan]

To fit the 1hdt in place of the 1hz there's a few considerations.

If you have the r151f trans then you should ditch it as it's derived from a car trans but used on the lighter side of the cruisers/prado/hilux, the 1hdt will destroy it.

If you have the h55f trans then it's more suited to the 1hdt but dont over strain it in 5th gear. The 1hz has fine spline 270mm clutch plate and the 1hdt has a coarser spline 300mm clutch plate. So you can't use the 80 clutch plate but can use the rest of the 80 clutch setup. Also for the h55f there's a terrain tamer transfer input gear that has a lot more spline surface so the main shaft has a better chance of not wearing the splines.

When I modded a 60 series trans with imported parts from Australia I changed to 1hz input shaft, used a 1hz bell housing, gearbox plus transfer rebuild kits, the terrain tamer transfer input gear and the part that linked it up was a fine spline 300mm clutch plate off a specific Isuzu light truck...

I have a lot of pictures and things I've done on my thread bj74 1hdt h55f combo thread in the garage section of the forum..

As you have a troopy then there's got to be enough space to fit the h155f out of an 80.. but either way if you want trouble free long term running then some gearbox work would benefit the conversion..