Toyota 1HDT vs 1HDFT (1 Viewer)

[sunrk]

I know there's a thread about 1HDFT vs 1HDFTE, but I'd like to focus more specifically on 1HDT vs 1HDFT as for a basic Aussie 80 series owner they are the most common engine choices for diesel upgrades. Many 1hz 80's still exist (like mine) with the original ex-factory motor. Standard upgrade path is to get a 1hdt, but 1hdft is another valid pathway.

There are hardly any people fitting other diesels to their 80's but some do.

So what technical reasons should one consider a 1hdt vs a 1hdft? Does the 1hdt have 'design flaws'? Obviously 1hdft is 24 valve vs 1hdt being 12 valve. For a DD vehicle like mine that rarely tows big loads and doesn't so much off road, and is already 30+ years old, is there any cost-effectiveness in opting for a 1hdft instead of 1hdt?

For normal use, is it of any relevance that the power curve of a 1hdft is supposedly better at higher rpm compared to that of a 1hdt (which is basically a 1hz block with a different head and air intake design I think)?

Cost-wise, a jap import 1hdt is around $10k and a 1hdft can be up to $15k. Aussie dollar prices.

I'm not sure I'd want to get the existing 1hz rebuilt and carry on as it's too old/worn to make a good candidate to fit a turbo kit onto. If I can find a good diesel motor place I will ask about potential cost range for a full rebuild.

In hindsight it probably won't matter which engine option I go for (even 1hz + t) - cost is still going to be upward of $10k and that's 2/3 of the insured value, but I'm not in a position to justify selling my 80 to get another one, so engine swap seems the only valid way to deal with the old motor.

 

[chapel gate]

is the old motor still going strong?

 

[sunrk]

It's going yes - strong is something I have no ability to correlate with anything else. Only 80 I've driven is my own.

 

[chapel gate]

keep on trucking then..

 

[chapel gate]

the 1HDT doesnt have any design flaws, BEBs aside.

 

[Stiles]

I've heard complaints about the heated air intake on FT vs glowplugs in the T. There is a specific month at which the BEB issue was sorted out (l think 2/92?).

Manual or auto? The mention that the manual is lower geared was news to me, meaning higher rpms at hiway speeds with the MT.

A newer engine is better, right, cause its newer? But not yet EFI. More valves is a good thing? Is the FT also direct injection?

 

[gilmorneau]

For normal use, is it of any relevance that the power curve of a 1hdft is supposedly better at higher rpm compared to that of a 1hdt?

No. The jump to 24-valve was a look forward by Toyota to the future of emissions requirements and thus the need for higher combustion efficiency. If 24-valves gives higher performance, it's minor and that was probably just a bonus to them.

So what technical reasons should one consider a 1hdt vs a 1hdft?

The earlier 12-valve motors are a bit simpler and more closely related to your 1HZ--injectors are more accessible, glow plugs instead of screen, etc. OTOH, there's the BEB issue with some 12-valve motors.

In some markets the 1HD-FT came with EGR which most people recommend disabling, otherwise it's hard to find fault with the 1HD-FT.

For a working truck, the 1HD-T seems the obvious choice to me, but it's not my truck. Lower cost, easier maintenance, almost the same performance, and a huge step up from a n/a 1HZ. Monitor the BEB thing and service as required.

 

[wedgetail]

I was going to stay quiet as I felt I said my piece in the other thread, but this prompts me to reply

No. The jump to 24-valve was a look forward by Toyota to the future of emissions requirements and thus the need for higher combustion efficiency. If 24-valves gives higher performance, it's minor and that was probably just a bonus to them.

The earlier 12-valve motors are a bit simpler and more closely related to your 1HZ--injectors are more accessible, glow plugs instead of screen, etc. OTOH, there's the BEB issue with some 12-valve motors.

In some markets the 1HD-FT came with EGR which most people recommend disabling, otherwise it's hard to find fault with the 1HD-FT.

For a working truck, the 1HD-T seems the obvious choice to me, but it's not my truck. Lower cost, easier maintenance, almost the same performance, and a huge step up from a n/a 1HZ. Monitor the BEB thing and service as required.

First point - the extra air flow the FT is capable of gives it much higher power potential. A tuned up FT goes much better than a tuned up T, in fact many say a highly tuned 1HZ-T can produce better numbers than a 1HD-T (it just won’t do it for long and will overheat). The increased air flow will also spoil up a bigger turbo quicker providing better low down response - all assuming optimum tuning. There’s much more of an advantage than just cleaner emissions - more air means more fuel can be added.

Apart from the valve bridge design, an FT is no more complex. Most people remove the inlet screen - it’s certainly not needed in Australia and people in Norway report east starting with no screen. Not sure what the 1HD-T without glow plugs is like though, I’ve always considered DIs don’t need any starting aid but I guess it doesn’t get that cold here.

Another significant factor is the FT pump is much better, smoother and more refined. When building an FT pump the IP shops give only a marginal discount when starting from a 1HD-T pump as opposed to 1HZ body. FT doesn’t suffer from the common 1HD-T problem of erratic idle especially on slopes, has smoother power delivery and is slightly more durable. The injection pressure is also higher, giving more power potential again.

The only disadvantage to the FT is cost. Personally I wouldn’t go to all the effort of fitting a 1HD-T when there are FTs out there - even if it’s just a work truck. What with the lack lustre performance potential, BEB issues and rough IP the FT is way it in front. Especially if you build an FTE-M…

 

[gilmorneau]

First point - the extra air flow the FT is capable of gives it much higher power potential.

Another significant factor is the FT pump is much better

The only disadvantage to the FT is cost.

I wouldn't argue any of this. Agreed on all points. I was only answering the OP's question re: a comparison of the two motors "in normal use", which I (perhaps mistakenly) interpreted to mean unmodified. In that instance, value for money goes to the 1HD-T in my opinion.

The OP seems to want more performance than his 1HZ offers (understandable) but doesn't hint at wanting to upgrade beyond a swap.

 

[wedgetail]

I wouldn't argue any of this. Agreed on all points. I was only answering the OP's question re: a comparison of the two motors "in normal use", which I (perhaps mistakenly) interpreted to mean unmodified. In that instance, value for money goes to the 1HD-T in my opinion.

The OP seems to want more performance than his 1HZ offers (understandable) but doesn't hint at wanting to upgrade beyond a swap.

Sure, and value for money when comparing stock motors probably tips it towards 1HD-T, the price of FTs is a bit over the top. Hence my mention of FTE-M, but I’d imagine this is even more pricey if not in Australia