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

[utleymu]

have to be creative for the rear engine cover. You are using a hiace late model 1kz that is with water cooled. It is a serious challenge to put 1kz into LH80 .

Yep, I'm going to need to create a new hump cover in the back. Right now I'm planning on using the original's flange, cutting out the hump, and welding in new panels.

Once I get everything running, the final fabrication cruxes of this project are the intake tubing from airbox to turbo, the snorkel, and this rear engine cover. I've got a tig welder for the intake/snorkel, but still need to learn how to use it. Hopefully with some persistence I'm able to get it done, but I may outsource some of this if I'm unable to.

 

[jdmkaizen]

As a fellow Hiace owner, following this cool build. Don't worry about updates, take your time and enjoy what's to come with the 1KZ!

 

[Dougal]

Would a front air/air intercooler be less work and more cab space than making a new dog-house?

 

[utleymu]

Would a front air/air intercooler be less work and more cab space than making a new dog-house?

I don't think an air to air would be less work, but ask me when I'm done. I like that the factory water to air setup is OEM, charge piping is tight and tidy. With how tight the spaces are in this truck, it would take a lot of work for me to get similar results snaking everything out front. But the main reason is that it leaves plenty of room for the A/C compressor, which I plan to add later. I don't think there would be any way to route the charge piping out to the front while still having room for the compressor.

I’m fine giving up a little cab space. The rear middle seat will be a bit less usable, but I never utilize it anyway. I am thinking about adding a small console with cup holders on top to make that area more functional. Here's a picture that shows what kind of space I'll be losing.

I'm not sure how difficult it will be to modify the cover. I'll be learning on the job. I've been thinking of cutting the sides out where I've marked in picture. Then I can bend the face and cut/weld new side panels. Would love to hear thoughts/suggestions on this if anyone has them.

 

[jcayce]

Edit. Will start a different thread in order not to derail this. It is an amazing build! Following closely.

 

[utleymu]

Figured I’m well past due for an update. We welcomed our first child into the world early in November, and with that, sleep, project time, and really time for anything else has been pretty limited. That said, there’s still been steady progress, and overall things are moving in the right direction despite a few setbacks.

The big milestone first: I fired the engine up and it ran great. Unfortunately, the celebration didn’t last very long. I quickly found an oil leak that traced back to a crack in the oil filter housing cover. I over-torqued the oil pressure sensor while installing it. Super frustrating, and completely avoidable on my part.

Adding to that, the specific oil filter housing cover for my engine is no longer in production. From what I can tell, there are at least two main variants of this part, Hilux vs Hiace. The Hiace version appears to have a water inlet for the turbo water outlet. I don’t see this same feature on the pictures of the Hilux versions, although the diagrams suggest the turbo water return may route differently. After some digging, I was able to find the correct part number used, located in Russia, and ordered it through a third-party service. I’m currently waiting for that to arrive. If that falls through, my backup plan is to order the Hilux version and figure out what modifications are needed to make it work.

I’m really really hoping I can remove the oil filter housing cover without pulling the injection pump. If anyone has done this before, I’d love to hear whether the pump had to come out or not.

On the engine side, once the housing is replaced, the remaining tasks should be fairly straightforward: pressure test and fill the intercooler water system, wire the intercooler pump and remaining gauges, then final packaging, wire management, and other cleanup items.

While waiting on parts, I was able to finish the manual shifters and get everything shifting smoothly. The system uses multiple bellcranks and rods. It was one of those setups that’s hard to visualize at first, but once you start working through it, it makes sense. It definitely took some trial and error to get all the stroke lengths and relationships right. I ended up using threaded rod and ball joints for the rods I replaced, and rebent one of the originl rods. I made adapter brackets to relocate the two lower bellcranks, adjusted the arm lengths on one bellcrank, and remade another bracket to move it about half an inch for clearance between a shifter rod and the intercooler tank.

I’ve also been 3D printing tubing sections to mock up the air intake and snorkel. I’ve been slowly practicing TIG welding, an hour here and there whenever I get the chance. I’m hoping to have a free day next weekend to actually start welding up the intake.

The airbox design itself is finalized; I just need to print it in ASA-CF filament.

So, in summary: I’m waiting on a replacement oil filter housing from Russia, and in the meantime I’m focusing on finishing the air intake. Once the intake and oil filter housing are done, I should be able to test drive the truck. After that, the remaining big items are the exhaust, snorkel, and modifying the doghouse—along with a long list of small miscellaneous tasks.

I haven't been taking many photos, but here are a coupel random pics:

Intake mockup:

Snorkel Mockup:

A couple of the engine:

 

[Tsvigo]

Figured I’m well past due for an update. We welcomed our first child into the world early in November, and with that, sleep, project time, and really time for anything else has been pretty limited. That said, there’s still been steady progress, and overall things are moving in the right direction despite a few setbacks.

The big milestone first: I fired the engine up and it ran great. Unfortunately, the celebration didn’t last very long. I quickly found an oil leak that traced back to a crack in the oil filter housing cover. I over-torqued the oil pressure sensor while installing it. Super frustrating, and completely avoidable on my part.

Adding to that, the specific oil filter housing cover for my engine is no longer in production. From what I can tell, there are at least two main variants of this part, Hilux vs Hiace. The Hiace version appears to have a water inlet for the turbo water outlet. I don’t see this same feature on the pictures of the Hilux versions, although the diagrams suggest the turbo water return may route differently. After some digging, I was able to find the correct part number used, located in Russia, and ordered it through a third-party service. I’m currently waiting for that to arrive. If that falls through, my backup plan is to order the Hilux version and figure out what modifications are needed to make it work.

I’m really really hoping I can remove the oil filter housing cover without pulling the injection pump. If anyone has done this before, I’d love to hear whether the pump had to come out or not.

On the engine side, once the housing is replaced, the remaining tasks should be fairly straightforward: pressure test and fill the intercooler water system, wire the intercooler pump and remaining gauges, then final packaging, wire management, and other cleanup items.

While waiting on parts, I was able to finish the manual shifters and get everything shifting smoothly. The system uses multiple bellcranks and rods. It was one of those setups that’s hard to visualize at first, but once you start working through it, it makes sense. It definitely took some trial and error to get all the stroke lengths and relationships right. I ended up using threaded rod and ball joints for the rods I replaced, and rebent one of the originl rods. I made adapter brackets to relocate the two lower bellcranks, adjusted the arm lengths on one bellcrank, and remade another bracket to move it about half an inch for clearance between a shifter rod and the intercooler tank.

I’ve also been 3D printing tubing sections to mock up the air intake and snorkel. I’ve been slowly practicing TIG welding, an hour here and there whenever I get the chance. I’m hoping to have a free day next weekend to actually start welding up the intake.

The airbox design itself is finalized; I just need to print it in ASA-CF filament.

So, in summary: I’m waiting on a replacement oil filter housing from Russia, and in the meantime I’m focusing on finishing the air intake. Once the intake and oil filter housing are done, I should be able to test drive the truck. After that, the remaining big items are the exhaust, snorkel, and modifying the doghouse—along with a long list of small miscellaneous tasks.

I haven't been taking many photos, but here are a coupel random pics:

Intake mockup:
View attachment 4070604

Snorkel Mockup:
View attachment 4070639
A couple of the engine:
View attachment 4070610View attachment 4070611View attachment 4070609

To remove the housing ,yes pump have to come out. Only the housings I have extra. Those with water coolant port. Without water coolant port is mostly for electric throttle body models. Older one have water passage at the throttle body. But if u need one I have it. Great progress btw.

 

[CarloniousFunk]

Congrats on the kiddo! Cool to see you get a 1kz into a HiAce, I've got the 3L in mine and a little more power really would make it perfect.

I was thinking about doing a similar snorkel setup on my truck but coming out the left side at the back of the cab out of the little notch, then going up to the roof. Seems like there's plenty of room behind the cab to either remount the stock filter setup or mount a Donaldson type filter. Curious what your thoughts are on having the intake that long? Also, what size tubing are you going to go with? 3"?

 

[utleymu]

To remove the housing ,yes pump have to come out. Only the housings I have extra. Those with water coolant port. Without water coolant port is mostly for electric throttle body models. Older one have water passage at the throttle body. But if u need one I have it. Great progress btw.

Oh man, if you have an spare I'd happily buy it from you! I'll reach out in direct message. Bummer that the pump has to come out, but I figured that would be the case.

Congrats on the kiddo! Cool to see you get a 1kz into a HiAce, I've got the 3L in mine and a little more power really would make it perfect.

I was thinking about doing a similar snorkel setup on my truck but coming out the left side at the back of the cab out of the little notch, then going up to the roof. Seems like there's plenty of room behind the cab to either remount the stock filter setup or mount a Donaldson type filter. Curious what your thoughts are on having the intake that long? Also, what size tubing are you going to go with? 3"?
View attachment 4070762

I think that's a great idea, I actually considered routing it there but on the other side. Unfortunately, the filler neck is right in the way. I'm still leaving it as an option, but the current location seems like the easiest approach.

I'm using 3.5" tubing for mine, it's the biggest I could reasonably fit in the space. I think bigger looks better, but 3" should be more than enough for the stock 3L engine. Might even be overkill. Maybe someone with more experience will chime in, but I don't think that distance in 3" tubing would present a significant choke point for a naturally aspirated 3L. Do try and keep the bends as gradual and smooth as you can, though.

 

[utleymu]

Replacement part from Russia finally showed up last week. Took long enough.

Spent a good amount of time cleaning and degreasing everything before installing it. Got it bolted up, replaced the surrounding components, filled with coolant and pressure tested. Found a small leak. Ended up being the filter housing cover to block seal.

Pulled it all back apart, cleaned the surfaces again, made sure everything was spotless, and torqued it carefully in sequence. Pressure tested again and it’s holding now, which was a relief.

After all that, the engine fired up and was able to get it to temp without any other noticeable leaks.

While I was waiting on the part shipment I finished up the snorkel and intake routing. It works, but I’m not 100% happy with the snorkel placement. It sits a little lower and further outboard than I’d prefer. If I had more time I’d relocate the fuel tank to the other side and run the snorkel down the back of the cab and along the frame rail into the rear of the airbox instead of entering from the side. That’s not happening right now, so this is where it'll live for now. Should be fine for my needs, but I may need to be mindful in some situations.

Don't mind the mess, or the polished finish - it will be getting painted black.

This week the goal is to knock out a few little things, fluids for:

• Diffs
• Transmission
• Transfer case
• Bleed clutch and brakes

After that I need to carve out some dedicated time to finish the rest:

• Pressure test and fill the intercooler cooling system
• Wire relay, intercooler pump, and gauges
• Modify the doghouse for intercooler clearance
• General wire and hose cleanup

I’ll likely have a shop modify the existing exhaust to mate to the new downpipe rather than build that section myself.

Overall, feeling good about it running and moving forward again. Hoping I can get the fluids sorted and then start stacking time to finish the remaining details and get it out for some real test drives.

 

[utleymu]

Big update: finally got the truck out for a couple short test drives this weekend. Still need to break in the diffs and generally shake everything down, so I kept it to a couple 15 minute drives around the neighborhood, but enough to start forming some impressions.

Overall, really happy with how it feels so far. The power is great, not sports car fast by any means, but a huge improvement over the L-series. Easily keeps up with traffic without feeling strained. I haven’t installed the camper yet and haven’t pushed it hard or given it much throttle, but even taking it easy the drivability improvement is immediately noticeable.

One of the biggest changes is actually the diff gearing. Going from 5.29 to 4.11 made a much bigger difference than I expected. It’s simply much more usable on road now. Pulling away from a stop is quicker and it needs fewer shifts to get up to speed. One thing I didn’t think about beforehand is that the gearing change threw the speedometer way off, so that’ll need to be addressed. Not sure yet whether an OEM speedo gear swap will get it close enough, or if I’ll need some kind of mechanical ratio adapter.

Shifting feels really good, although the shifter sits a little further forward in neutral than I’d like. I may adjust some of the linkages to fix that.

Clutch feel is very good. I had a bit of trouble bleeding the system initially, but a reverse bleed did the trick. I also needed to adjust the master cylinder pushrod because the clutch wasn’t fully disengaging until the pedal was on the floor.

The truck sounds really good right now, but definitely a bit loud as I haven't connected the exhaust yet. Planning to take it to a muffler shop this week to tie the exhaust into the dump pipe so I can get that finished up.

I went with a 76°C thermostat since that’s what Toyota specs for the Hiace vans and seemed like the closest match for this cabover application. Temps are currently sitting a bit low, mostly in the 170°F range, but ambient temps are still fairly cool here so I’ll keep monitoring as I put more miles on it. If needed I can switch to the more common 82°C thermostat later.

Haven’t done any sustained driving or highway pulls yet, so I don’t have meaningful data on EGTs, intake temps, intercooler effectiveness, etc. The mechanical pump I received was originally tuned for a 21 psi max boost target, but I added a shim to the boost fuel pin and plan to start conservatively around 16 psi. From there I’ll see how my intake temps, egt's, etc. are and adjust accordingly with more shims and/or more/less boost.

Right now, the only issue I've noticed is a small leak at the power steering pump. It looked like it was coming from the outlet to overflow, so I put a better clamp on will monitor.

Modifying the doghouse cover ended up being more tedious than difficult. The worst part was dealing with the sound deadening material I had on there. I caught some with the flap disc and it spread the sticky mess everywhere. Took longer to clean up than the cutting and welding. Fitment came out decent and there are plenty of welds, but I still used a generous amount of seam sealer just to be safe. Didn’t spend much time on cosmetics since it will all be covered anyway — just a coat of black chassis paint for protection. Ugly but functional:

Here’s a photo of the finished airbox showing the snorkel inlet and outlet to the turbo.

Airbox gets covered by the wheel well mud flap/rock guard.

Feeling pretty stoked to have it back on the road, it's been a long time coming.