12H-T or LQ9 discussion.... (1 Viewer)

Spook50

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For a while I've been planning on (when I can afford it) an LQ9 swap with an NV4500 behind it. I still can't shake that little nagging desire to keep it Toyota though, and diesel is still a tempting option. Been wondering about a 12H-T with my H55F behind it, which would also involve the cost of regearing my diffs for highway driving (I turn 2700 RPM at 70 MPH with 33" tires and my stock 4.11 gears. Feels great around town getting up and moving, but since the 12H-T makes its peak power at 1800 RPM I would need to go down to maybe 3.73 gears?). I expect the Vortec conversion would out the door cost more than the 12H-T conversion (which could be offset by regearing). Someone familiar with both conversions, please correct me if I'm wrong. So if cost isn't a factor, what direction would you guys go, and why?



One downside of diesel is that diesel fuel in the US doesn't have the lubricity of diesel sold in other countries, so without additives, there is more wear than there would otherwise be if I ran it here in the US. I expect I would still get more life out of a 12H-T than an LQ9 though, regardless.
 
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I cant help you with total conversion cost but I'm curious....have you priced a landed Toyota diesel versus a junkyard LS? From what I understand 12HTs come at a high price and would typically have high kms? Once again just curious.
 
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Sorry glanced over your "cost is not a factor" comment. Toyota diesel all the way and if you felt the need to regear put lockers in at the same time if you don't have them. As far as why - range on a tank of fuel and honestly the coolness factor. But I'm a diesel head.
 

AussieHJCruza

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If it's a daily in the states, LQ9 (yes it pains me to say that, but it's true)
If it's not a daily, then definitely 12HT, there's something about a mechanical diesel that nothing else provides. As far as gearing, I'd drive it first before doing something like gearing, the 12HT isn't a powerhouse stock, so wouldn't suggest major mechanical changes like gears until you see how you like it. In my opinion, H55 first is about right with 35s and 4.11, it's too short most of the time with 33s, so on the same ratio, 33 and 3.7 is numerically similar and probably about right.
 

bcsteel

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What about a 1hdft? More power and more parts available. That being said I have a 12ht and it’s pretty darn good
 
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12H-T with H55F and 4.11s works just fine with 33s. RPMs are 2700 or so at 65-70 mph. 20+ mpg. Have not had any issues with diesel in the states runs like a champ. If you only want a road rig then 3.73 would be better but really hinder you off road.

If money was not an issue i would get a newer toyota diesel just for parts availability. But the 12H-T is an awesome engine.
 

MANUCHAO

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I got an lq4 on mine..
But if $$ was no issue, and up in WA...
I would go..
1HD-FTE and H151...

LQ9 tuned would be you loads of power....
But same can be said for the diesel counterpart when tuned...+ Fuel range....
 
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i have an intercooled 1hdt h55 33 inch tires and 4:11. i absolutely love it. 1st is a little short but over drive is just right. either way it’s way better than the skushbox. yes cost was a bit of a bummer but now that i have it as my daily driver i wouldn’t change back. i can pull a boat all day and even towed a few cruisers and my chevelle on a car hauler (5000ish lbs) and it had no troubles as 90km/hr. i think the 1hdt parts are a little easier to source than the 12ht. just food for thought.

still waiting to get my g turbo on it!
 

OSS

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The 12-HT is a 1980s era engine. Same as the 2F. On paper it's specs are very similar to the 2F. The LQ9 is 20 years younger than the 12-HT. Finding parts for the 12-HT is like finding parts for a Model T. Unobtainium.

Shoehorning a 12-HT into a 60 series was THE thing to do about 20 years ago for wealthy hobbyists- but now? I'd take it off the wish list (or ponder list)
 

Spook50

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i have an intercooled 1hdt h55 33 inch tires and 4:11. i absolutely love it. 1st is a little short but over drive is just right. either way it’s way better than the skushbox. yes cost was a bit of a bummer but now that i have it as my daily driver i wouldn’t change back. i can pull a boat all day and even towed a few cruisers and my chevelle on a car hauler (5000ish lbs) and it had no troubles as 90km/hr. i think the 1hdt parts are a little easier to source than the 12ht. just food for thought.

still waiting to get my g turbo on it!
There's a possibility I hadn't considered. How's it do for long hauls up the passes? Lots of long uphill grades where I drive. Would be about 75% road and 25% moderate (not hard) wheeling.
 

bottombracket

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Sooooo...I have an HJ61 that I’m just getting back on the road after a two year hiatus for a motor rebuild. The 12HT is an awesome engine. It grunts, it snarls, it has so much torque. But as @OSS says, it is 30 years old and parts are rapidly becoming NLA. I had @roma042987 rebuild mine prophylactically because it had 465,000 km on it. It should last another 30 years after his awesome work. But, parts are rapidly disappearing. Also, its power band is relatively narrow and square - it is super choppy and grunty. That said, I love the hell out of mine and I will never, ever sell it.

I am having @orangefj45 FJ 45 shoehorn a 1HDFT into another 60 series for me. It will be more built on 35’s or 37’s. The 1Hx’s are so much smoother, and remember, Toyota is still making the 1HZ brand new today. Parts availability from multiple sources is much easier. Did I also mention that they are smooth like butter?

Food for thought, from another diesel lover.
 
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There's a possibility I hadn't considered. How's it do for long hauls up the passes? Lots of long uphill grades where I drive. Would be about 75% road and 25% moderate (not hard) wheeling.

with the intercooler and a conservative foot i can climb hills at highway speed and never worry about my egt. if i have a trailer on i’ll keep an eye as they can work their way up. i did a few really steep hills with a loaded truck and military trailer going through utah and it was snorting some black and getting hot so i just slowed down (hence getting the g turbo). i took a trip from my home to grand canyon with my family hauling my military trailer last year. it was about 6500km round trip. i cruised 70mph on interstates more because of the trailer than anything and it just cruised. didn’t feel like i was going to blow anything like with my old 3FE. I hauled a 3500 lb camper with it. into a hot headwind i struggled to keep my temps down so i sold the trailer. it’s not a 3/4 ton that can haul heavy loads or a big trailer with wind drag but for what i need it’s great. i daily drive it and get about 550-600km per tank. that’s with all this on it!

943B69FE-E851-4626-860C-052117EA1C6F.jpeg
 
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I asked myself the same question and was planning to do an LS if/when the 2f ever quit. I stumbled on an FJ62 that already had a fresh 1hdt swap and that changed my mind. The Toyota diesel still hangs on to that old school Toyota nostalgia/feel but would run circles around a 2F/3FE. It’s my daily and I love driving it. Steep mountain pass, usually don’t even have to downshift 4th or 5th gear and it jams right up. This is with a factory ct26 and tuned to factory specs. If you ever find yourself in SW Washington, let’s go for a spin.
 

Spook50

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with the intercooler and a conservative foot i can climb hills at highway speed and never worry about my egt. if i have a trailer on i’ll keep an eye as they can work their way up. i did a few really steep hills with a loaded truck and military trailer going through utah and it was snorting some black and getting hot so i just slowed down (hence getting the g turbo). i took a trip from my home to grand canyon with my family hauling my military trailer last year. it was about 6500km round trip. i cruised 70mph on interstates more because of the trailer than anything and it just cruised. didn’t feel like i was going to blow anything like with my old 3FE. I hauled a 3500 lb camper with it. into a hot headwind i struggled to keep my temps down so i sold the trailer. it’s not a 3/4 ton that can haul heavy loads or a big trailer with wind drag but for what i need it’s great. i daily drive it and get about 550-600km per tank. that’s with all this on it!

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That's exactly what I would love to have. No plans at this point to pull any heavy trailers, but there will definitely be weight on my truck and I'd like to have the ability to tow if need be. Very similar to your setup actually. My end goal is an expedition rig for long trips and camping.

What difference is there in the G turbo versus your current (OEM?) one?

@Rustic76 I'd love to check it out next time I'm on the west side. I have friends in Snohomish so I could probably make a detour on one of my trips over.
 
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If your converting to a Toyota diesel 1hdt ft fte a 1hdt is the same price as a 12ht makes more power and exhaust is away from your steering box booster etc for you lhd.
I do love the way the 12ht starts up in half a turn every time. 21-23 mpg.
 

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