Hiace / Dyna Engine Swap - L Series to 1KZ in a Cabovers (1 Viewer)

[utleymu]

I've been thinking about an engine swap in my LH85 cabover Hiace truck for a while now. The reasons will be obvious if you've ever driven a truck with an L series engine. They're painfully slow and gutless, especially when you add even the lightest of campers.

I started out by slapping a turbo on the original motor — and to be fair, it actually woke the truck up pretty nicely in terms of power. But the install was a pain. The tight cabover layout combined with the manual shifter linkages made the packaging super awkward. Everything felt crammed, and it never quite fit right. In the end, the whole setup pushed the little engine past its limits — ended up popping it and losing compression on cylinder #4. So yeah… good power, but not worth the headache or the blown motor.

Looking back, I kind of wish I’d just gone straight to an engine swap from the start. Would’ve saved some time, money, and a blown motor. There’s basically zero solid info out there on engine swaps for these cabover trucks — it’s a bit of a black hole. That said, I did find a few threads about folks going from L series to 1KZ or 1KD in Hiluxes, and a couple of mentions of it being done in vans. Nothing detailed though.

This project is way outside my comfort zone, but I’m jumping in anyway. Figured I’d document the process here — partly to give back and maybe help the next person, but also to get feedback and guidance from those of you who’ve been down this road before.

Life’s a little hectic right now, so updates might be a bit slow, but I’m committed to seeing this through.

Why the 1KZ?

There's no perfect engine, each choice has pros and cons, but the 1KZ is far from the holy grail of engines. I was not looking for crazy horsepower — just wanted to go from “ultra-slow” to “normal slow”. My main criteria:

• Ease of swap – first time doing something like this.
• Keep it diesel.
• Toyota power only. Just seems wrong putting anything else in this rig.
• Compatible with my R-series trans.
• Mechanical over electronic. Simplicity rules, no complicated electronics.
• Reasonable power and reliability.
• Compact enough to fit the cabover engine bay.

Engines I Considered:

1KD

• Great motor, good power, solid rep.
• Small footprint (same block as 1KZ, however I think the head is taller which could potentially be an issue)
• Bolts right up to R trans.
• BUT… common rail, needs electronics. This would significantly increase difficulty of swap.
• Also pricey and rare in the States.

1KZ-TE

• EFI from factory, but easy mech pump conversion via KRAE in NZ.
• Less power than 1KD but still plenty. 120-130 hp at wheels seems like a sane reliable goal with intercooler, adequate exhaust and intake.
• Very similar footprint to the L series. Same width and length, only slightly taller.
• Direct bolt-up to my R trans with the right bellhousing.
• Availability and price is very good
• Known weak point: cylinder heads can crack if cooling system is neglected. Still IDI turbo.
• But with maintenance? They hold up.

Mercedes OM605

• Tempting. Mechanical injection, solid power, diesel cult status.
• Downsides: Not Toyota. Expensive. Long. Hard fit (probably too long and too tall). Adapter needed for R trans.

TDI

• Small, compact, big owner community, lots of info out there, lots of parts out there.
• Not Toyota, though. And smaller displacement could be stressed in a heavy rig.

Toyota B series

• Legendary reliability
• Direct Injection options
• Unfortunately too big, too heavy, too rare, too expensive, too complicated to install

Why I Picked the 1KZ:
Checks most of my boxes:

• Easiest option to install.
• Toyota badge.
• Mech pump option.
• Plenty of power for my needs.
• Simple, reliable, and fits the space without major re-engineering.
• Not perfect but I think it's a good OEM+ option

Sourced a later-model Hiace 1KZ with the factory water-to-air intercooler (bonus!) for a very reasonable price.

I also have a mech pump and high-flow turbo from KRAE on order, planning to keep it mild — focus is on reliability and efficiency, not big boost.

Also will be doing:

• Injectors
• Glow plugs
• Timing belt
• Water pump
• Full gasket set and general freshening up

Build Plan:
Breaking it into phases so I don’t get overwhelmed:

• Engine mounts & general fitment
• Packaging – shifter linkages, radiator, etc.
• Engine maintenance
• Final install
• Plumbing & wiring – coolant, intake/exhaust, alternator mod (external regulator to internal, sensors, etc.)

 

[utleymu]

I was dreading having to pull the engine from this truck, but it actually ended up being way easier than I imagined. Although you need to pull it out through the passenger door, everything is easily accessible and very straightforward. A 2 ton crane with the exteneded reach and a swivel hook is definitely necessary.

Next step was to make the engine mounts. I decided to design them, then test with 3D printed mounts before ordering the steel from Send Cut Send and welding them up.

I knew the Hilux guys had it easy — swap from L series to 1KZ usually just means shifting the mounts 40mm. Was hoping for the same… no such luck.

The Hiace 1KZ mounts I got are wider and identical left/right, while my chassis needs different spacing/height for each side. I started out by designing some mounts that would position the block with the top mount holes at the same position as the stock 2L. After a test fitment, this was definitely too low. I raised the block 25mm, and the fitment seems bang on. Plenty of clearance on top and the engine sits at the same 4.5 degree tilt I measured on the stock one:

I was a little nervous trusting any weight on the 3D printed mounts, but they actually held up pretty well and allowed me to bolt up the transmission and verify alignment was good.

The only issue is the oil pan almost touches the front diff mount at the points marked below (note, I have the engine shifted over a bit in the picture, but it's closer when mounted):

I'm planning on grinding out that marked area on the diff mount. If anyone thinks thats a terrible idea, or has suggestions on strengthening it, let me know.

I'm currently waiting on the steel from SendCutSend to arrive, then I'll be able to weld up the mounts and fully test fit all components.

As an aside, here are some known obstacles I'll need to overcome (so far):

• Alternator is internally regulated vs. stock external. Need to wire that properly — found a few MUD threads I’ll reference.
• Shifter linkage mount needs a bracket moved and a new one fabbed. Hoping the linkages have enough slack to compensate.
• Water-to-air intercooler sits high/rear — going to have to trim the rear hatch panel above the bellhousing for clearance.
• Fan-to-radiator clearance is going to be tight, likely need to move radiator .5" - 1" forward.
• Radiator plumbing – exit hose is on opposite side. Might try to get the radiator modified to match the 1KZ layout.
• Coolant lines and heater core routing still TBD — Not sure what custom options are available for this.

Life’s busy so progress is whenever I can sneak time, but the motor’s out, the mounts are underway, and I’m getting a better feel for how everything needs to land.

 

[aztoyman]

I'm going to follow along just because it's an interesting project. Sounds like you have a reasonable plan. It's always seems to be the little stuff that takes the biggest time in projects like this. There's always a way though.

Can your original externally regulated alternator just swap on to this engine so you don't have to alter your harness? Not that a minor mod to the wiring is a big deal.

I don't think the slight trimming of that mount would be a problem.

Good luck with your project!
Scott in AZ.

 

[utleymu]

I'm going to follow along just because it's an interesting project. Sounds like you have a reasonable plan. It's always seems to be the little stuff that takes the biggest time in projects like this. There's always a way though.

Can your original externally regulated alternator just swap on to this engine so you don't have to alter your harness? Not that a minor mod to the wiring is a big deal.

I don't think the slight trimming of that mount would be a problem.

Good luck with your project!
Scott in AZ.

Hey, thanks for the reply. I want to use the 1KZ alternator because it's double the amperage (70 vs 35) and the 2L has a vac pump mounted to the back, whereas the 1KZ uses a standalone vac pump. I'm hoping this is the only electrical obstacle I have to work through.

Between all the little things, and waiting on random parts I'll inevitably need to order, I'm definitely anticipating that this project will take a bit of time. I'm also really busy and having my first child in November, so it won't be my top priority. However, I do love this truck and need a family camping rig, so I'll eventually get it finished one way or another. It's like eating an elephant, one bite at a time.

 

[fenderfour]

following....

 

[Dougal]

What's this "high flow" turbo? The stock turbo is a CT12B which is based on the MHI turbos but has a really old and inefficient turbine design. That's the part that needs fixed. A bigger compressor will just risk surge.

 

[utleymu]

What's this "high flow" turbo? The stock turbo is a CT12B which is based on the MHI turbos but has a really old and inefficient turbine design. That's the part that needs fixed. A bigger compressor will just risk surge.

The turbo I'm using is this one:

Toyota 1KZ-TE Turbo Hi-Flow - KRAE 4x4

KRAE 1KZ-TE Turbo Hi-Flow 100% bolt on unit, no modifications needed. Very efficiently matched turbo for the 1KZ engine. Super responsive! More details below.

www.krae4x4.co.nz

It's from the same company I ordered the mechanical pump from. I spoke with them, and they’ve had direct experience with the factory water-to-air intercooler I'll be running. So I figured I’d let them set the pump based on their experience and the build notes I sent over — at least as a baseline.

I was kind of on the fence about the turbo, but since it's a drop-in replacement and supposedly a more modern, efficient design, I figured I might as well upgrade while everything’s apart.

Are you familiar with this shop? They're based in New Zealand too.

 

[Dougal]

The turbo I'm using is this one:

Toyota 1KZ-TE Turbo Hi-Flow - KRAE 4x4

KRAE 1KZ-TE Turbo Hi-Flow 100% bolt on unit, no modifications needed. Very efficiently matched turbo for the 1KZ engine. Super responsive! More details below.

www.krae4x4.co.nz

It's from the same company I ordered the mechanical pump from. I spoke with them, and they’ve had direct experience with the factory water-to-air intercooler I'll be running. So I figured I’d let them set the pump based on their experience and the build notes I sent over — at least as a baseline.

I was kind of on the fence about the turbo, but since it's a drop-in replacement and supposedly a more modern, efficient design, I figured I might as well upgrade while everything’s apart.

Are you familiar with this shop? They're based in New Zealand too.

Sounds like they've just put a bigger compressor in it. I think you can do better than that. The turbine will still be old and inefficient and that's where your response comes from:

Turbocharger Turbines.

Here is a short history of turbocharger turbines and their performance traits as interpreted by myself. All I can say about the accuracy of this data is it makes sense to me and I follow it with my own hard earned money. If anyone knows better, feel free to correct me. Turbocharger turbines...

www.4btswaps.com

Here's a CT12B turbine. It's a paddle wheel from generation 1:

A MHI TDO4 turbo will give you a gen2 turbine which is much better at a lower cost. A gen3 11 blade TD04HL turbine wheel will do even better.

 

[janyyc]

Looking forward to seeing this swap!

 

[Tsvigo]

congratulations, welcome to the KZ world. hiace is not rare it will be easy swap. if you need some bits and pieces. i might still have some. like the bell housings.
replying to your idea on 1KD swap, i do not recommend it. difficulties is 100 lvl. unless you are like me, my 1kd electrical took me solid 1 month 8hr/day work. break downs 2-1/2weeks to figure wires for it to start and idle. once i successfully done that, the rest are just like eating peanuts.

 

[Tsvigo]

Sounds like they've just put a bigger compressor in it. I think you can do better than that. The turbine will still be old and inefficient and that's where your response comes from:

Turbocharger Turbines.

Here is a short history of turbocharger turbines and their performance traits as interpreted by myself. All I can say about the accuracy of this data is it makes sense to me and I follow it with my own hard earned money. If anyone knows better, feel free to correct me. Turbocharger turbines...

www.4btswaps.com

Here's a CT12B turbine. It's a paddle wheel from generation 1:
View attachment 3932218


A MHI TDO4 turbo will give you a gen2 turbine which is much better at a lower cost. A gen3 11 blade TD04HL turbine wheel will do even better.

triton tf035. the vgt one....... 04HLA. thats about it. other td04 is just history to me.

i've been breaking stuff since 2002.......

 

[Dougal]

triton tf035. the vgt one....... 04HLA. thats about it. other td04 is just history to me.

i've been breaking stuff since 2002.......

Probably similar to the one I have on my Dmax. That one overboosts to almost 30psi on hard acceleration. Which is interesting but not a big deal. Steady state load it's only ~15psi.

Interestingly fixed geometry turbines are more efficient than variable vane ones.

 

[PBcuiser]

Sweet project! On the topic of radiator mods, a local shop should be able to move around inlets and outlets no problem.

 

[utleymu]

Been a while since I’ve posted an update. I’ve been puttering along slowly while waiting for parts to come in from around the world.

All the important stuff is finally here and I was able to drop the engine in, hopefully for the last time, and start working through the smaller details.

I got my mechanical pump, turbo, and injectors from KRAE in New Zealand. Installed the pump and timed it to their recommended spec. While I was at it, I also replaced the water pump, timing belt, valve cover gasket, and thermostat. Tried figuring out if the turbo's turbine is an upgraded gen 2 or not, but I couldn't tell. It didn't look like there was a paddlewheel, but it was hard to tell.

Engine Mounts
I had already welded up some engine mounts, only to realize the rubber isolators for my rig have been discontinued. Since they were over 30 years old, I really wanted to replace them. I ended up ordering some mounts used in 1KZ Hiace and Hilux models, as well as some newer vehicles. They were a close match to the old ones, but still required me to remake the mounts.

Clutch/Flywheel
I struggled finding a reasonably priced flywheel. They’re all heavy and expensive to ship overseas, but I ended up getting one from nzautomotive.co.nz. It was the cheapest option I could find and had the added bonus of supporting the larger 1KD 275mm clutches. Unfortunately, the bore was just slightly too small (maybe 0.05mm), and I couldn’t slip it onto the crank. For now, I’ve installed the transmission without the clutch/flywheel just to keep making progress. I’ll take the flywheel to a machine shop this week to get it sorted. I'll be using a 1KD heavy duty clutch by NPC. I also sourced a bellhousing, clutch fork, and slave cylinder.

Airbox
I’ve decided to place the airbox behind the front wheel well, in front of the fuel tank. This avoids having to cut the body for the snorkel and air intake. I still think the spot where the stock overflow tank sits might look cleaner and more OEM, but I’d have to use a smaller air filter and cut a big hole in the truck. That might be a later project. For now, I’m using a foam filter from UniFilter Australia. It’s 5.5" in diameter, 5.5" long, with a 3" flange. I printed a mock-up airbox that’s about as small as I could reasonably make it. I could move the fuel tank back about an inch if needed, but I think it fits well as-is. I’ll be 3D printing the final version in ASA-CF. I think 3D printed ASA should be fine since it will be placed behind the wheel arch cover and protected from rocks flung by the tires.

Radiator
I’ve got the radiator moved forward a bit and in a good place. I also 3D printed a mock-up radiator fan shroud. It still needs a few revisions, but I’ll have the final version printed in nylon by an online service since it’s too big for my printer. Still not sure if I'm going to go through the trouble of having a radiator shop place larger inlet/outlets and move the outlet from the front to the rear. I'm also not sure about the best way to go with the upper/lower radiator hoses. Seems like my options are to bend a wire of the routing I want and try to find a random oem hose that matches, or get a muffler shop to bend some aluminum tubing. From what I can tell, there aren't really any good DIY custom coolant hose options. If anyone has suggestions or recs, I'm all ears.

Intercooler
For the water to air intercooler, I've decided to use two small radiators instead of one large radiator. I wanted to avoid blocking the main radiator and I found a motorcycle radiator that fits in the left and right corners of the bumper. I know it won't be as efficient, but I'm hoping they'll do for my needs.

Wiring/Electronics
I was able to use my old oil pressure sensor in the new engine. The coolant sensor has a larger thread, so I’ll need to get an adapter for that one. I’ve looked into the wiring for the alternator and bypassing the external regulator seems pretty straightforward. I’ll share more once I get into that part. Haven't even thought about the glowplugs yet, but I'm hoping I'll be able to use my existing wiring/system for them.

Shifters
Spent a bit of time on the shifters too. I used some threaded rod and lawnmower-style ball joints to get the side-to-side shifter working. I thought I wouldn’t need to touch the other shifter, but turns out it interferes with the downpipe, so I’ll have to rework that as well.

Still a million little things to do, but feeling pretty good about the swap so far.

 

[utleymu]

I also wanted to ask if anyone knows what the nipple in the blue circle is for? This is on the oil cooler/filter area.

I know the green circle is an oil drain, in the manual it explains to use it to drain residual oil during oil filter changes, so pretty sure I can leave that uncapped. However, I haven't been able to find any info on the other nipple. It looks like it might be coolant or vac, hoping I can just cap it off.

 

[TheBussman]

I also wanted to ask if anyone knows what the nipple in the blue circle is for? This is on the oil cooler/filter area.
View attachment 3963742

I know the green circle is an oil drain, in the manual it explains to use it to drain residual oil during oil filter changes, so pretty sure I can leave that uncapped. However, I haven't been able to find any info on the other nipple. It looks like it might be coolant or vac, hoping I can just cap it off.

the blue circle is a coolant drain. loosen that bolt right next to it and coolant will drain out.





for the radiator: hose routing: they make aluminum tubes with bends in a size that's close enough. maybe 1.5" or so. cut those up so they fit hopefully you can get what you need done with just one piece if you can't then cut two pipes and weld them together. If your can't weld aluminum just put another hose between them.

 

[utleymu]

the blue circle is a coolant drain. loosen that bolt right next to it and coolant will drain out.





for the radiator: hose routing: they make aluminum tubes with bends in a size that's close enough. maybe 1.5" or so. cut those up so they fit hopefully you can get what you need done with just one piece if you can't then cut two pipes and weld them together. If your can't weld aluminum just put another hose between them.

Thank you! That's good to know