Cummins r2.8 swap, 1975 FJ40 (1 Viewer)

Nov 16, 2010


Enhance 😁:

"If at first you don't succeed, destroy all evidence you tried"

Lurking and searching a lot since last summer, I saw a bunch of build threads peter out into nothing either because the builder loses interest, or finds out it's too much project, or gets it done and it's so disappointing they want to forget about it. And I know how that feels because all three of those happened to me on FJ40 Project #1 (2003-2010).
So I wanted to wait until I had something worth sharing before committing to a build thread, and three weeks ago I reached that point.
I drove this truck on the road for the first time in a year, and it was everything I hoped it would be.

1975 FJ40
Done by previous owner: Carb SBC with original 4 speed & TC, shackle reverse, power steering (Scout II, resembles FJ60 but isn't), extra gauges, mystery wires

Cummins R2.8
NV4500 with Quickdraw bellhousing and 1969 TC with Advance Adapter Adapter
Dakota Digital Gauges
Rewired the whole thing
Brake lines needed some help
Needed a new heater setup as a butterfly effect consequence of the steering box
New fuel tank because of the giganto transmission
There's a Dakota cruise control box bolted in there that I haven't gotten around to wiring yet.

Last fall before the actual engine swap, driving it for the first time in 4 years, I got serious about investigating the "Brakes suck and handling sucks but that's just how FJ40s are" story.
Because if that was just how FJ40s are, I was going to bail on this project before it began and put the whole fleet on CraigsList.

Determined that the brake booster was ruined by leaking brake fluid, and rather than try to rebuild the original got one from a 1993 4Runner, which is almost a direct bolt in.
Now the brakes are awesome. Ok they still pulse and pull to one side, but that's a lot better than "Smash full strength and they barely work."

Also learned about caster and axle shims, and 4 degrees later it was like a whole new truck. Instead of sailing into the weeds every 40 feet I could take my hands off the wheel at 60 mph and it tracked perfectly.

So here it is:

If there's anything specific that you want to know about this project, ask away!
Otherwise, I guess I will get to it in the order that I get to it.
Nov 16, 2010
A bunch of this thread is going to be here's what I did and why I would not do that again, but overall I'm really happy with the end result.

NV4500 vs H55
Three reasons I would have not gone with the NV, and two of them are: it's big!
It's tall. If you don't want to cut or lift your tub, it's going to hang below the frame.
Before tub cutting:

Accepting that this is going to be ugly

It's not a show truck or a restoration or even a restomod though. It already had some hokey butchering going on, and now it's going to have some different hokey butchering.

End result of that choice

It's in there, and none of it hanging below.

It's long.

So the cross tube obviously can't stay there and had to come out, and I replaced it with a transmission crossmember which is a heavy piece of channel and bolted with clamshell mounts to both sides of each frame rail
Now that I'm doing this thread I realize how many things I don't have pictures of, I'll try to get more in the next few days.

The rear drive shaft ended up being about 4" long and kind of steep, so I needed to come up with some sort of double cardan shaft.
Searching here led me to first gen Tacomas, and the auto salvage yard about a mile away. The two piece rear drive shafts have a dc joint in the center. I have no idea why, because it's not a wild angle on those trucks, but they do.
95 to 04, newer than 05 is a standard u-joint.
Prerunner or 4x4 only, 5 lug 2wds have a regular u-joint. That one took a couple of days to straighten out with the parts guy, and I had to find a Tacoma on a used car lot and get a picture of the joint before he believed me.
And extra cab or longer, regular cab will probably have a one piece shaft with the standard joints.

So having bought the drive shaft, the easy part was over. Next up was pressing the studs out of the parking brake drum, drilling new holes offset 45 degrees, and opening the holes in the joint up a tiny bit.
The spline is the same between the Tacoma and FJ40, so that part was kind of easy, I just used the original half at the axle and then took it to the local driveshaft shop to get it shortened.
I'm still getting around to shimming the rear axle to get the second joint angle correct, because it's definitely not.
Nov 16, 2010
Mishimoto intercooler from Summit, 28x7.5x2.25"




I used Intercooler Pipe Fabrication for a bunch of stuff. Mostly the silicone intake parts, but also the radiator plumbing and they have a good selection of stainless tube I used for the exhaust.
Everything from the turbo to the intake is 2.5" and I used the 2.5" clamps on most of it, but the intercooler inlets are a very tight fit so I needed to use the next size up clamp on those.

Used a 3" to 2.5" reducer elbow from the Cummins intake tube to another aluminum tube, and then a 2.5" to 2" elbow from there to the turbo inlet.
The MAF sensor...doesn't quite fit on the supplied tube:

So I altered it by about 5"

I'll get a picture of it later on, but that tube also has a bracket welded to it to bolt to the fender
Nov 16, 2010
Out with the old

In with the new

Mocked up where the hood would close at

Don't want to leave any axle clearance on the table if I don't have to

Farmstrong universal engine mounts

Painted the mounts yellow because why not.
Making the towers was kind of an ordeal because we would get one side mocked up and move to the other side without realizing that the forklift holding the motor up was settling.
We got it done by making the frame piece and the top piece, and MIG zapping a small strip between them quickly while the motor was in the right spot, and then pulling them out and making and tig welding the whole box structure.
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Nov 16, 2010
Making the fuel tank, part 1

Borrowed a friend's Harbor Freight level sheet metal brake, but it wasn't hurky enough for 0.100" Aluminum, 4 feet wide so we went to another friend with a bigger brake that did the trick.




Nov 16, 2010
Fuel tank part 2


It ended up at 18 gallons exactly.
We used the Classic Instruments tube sender and it matched up with the Dakota dash perfectly. Read empty when empty, read full when full, now reads a little under half after driving 240ish miles, so fuel economy is looking like it might turn out as advertised.
Nov 16, 2010
Cooling system
"The R2.8 CM2220 R101B engine is designed for use with a positive fully deaerating cooling system."

"A fully deaerating cooling system enables trapped air in the cooling system to be properly purged. The cooling system is comprised of a radiator, deaeration tank, fill line, and vent lines. The pressure cap on the deaeration tank should always be the highest point of the system. All vent lines must continuously run uphill until they connect into the dearation tank."

Ok, what? This is one of the chapters where I gotta be honest, the other builds everywhere on the internet weren't very helpful, and neither were the videos from Cummins. Googling "deaeration tank" showed a schematic of what Cummins does in theory, and no real world examples. It took a few days of deciphering, but I'm pretty sure I ended up with what they meant. If not, then I'm following the rule that the fastest way to get the right answer isn't to ask, it's to post up the wrong answer.

Deaeration Tank:
Water Header Tank, Vertical, 8" H x 4" Dia, without Cap - Pegasus Auto Racing Supplies

I cut and rewelded the mounting tabs and was able to use threaded holes that were already in the firewall. The top inlet needs to be the highest point in the pressurized part of the water system, and center of the engine bay near the back is what the hood allows.
If the oil filter, fuel filter and grid heater solenoid locations on the edge of the picture look familiar, it's because I read DDelong and Sheck's builds and thought "Well, not going to beat that!"

Somewhat plumbed in:

The 3/4" hose out of the bottom of the tank goes to the aluminum piece connecting the original radiator and the engine water inlet. Lots of bending reducers from silicone intakes and wire hose clamps from Amazon.

More plumbed in. The thermostat housing clocks 120 degrees from where it's installed at the factory, which is nice because then it points directly at the radiator.

The hose is tight and a huge pain to get on both the radiator and the thermostat housing, so I connected them once while they were out of the truck and in an easy position, and then the aluminum coupler between them is easy to go on and off with for removing the radiator.
Also pictured, the Dakota temperature sender, but the M12 adapter they included was the wrong pitch so I had to find another one.

Reposted photo of the end result, mainly showing the air outlets in front of the thermostat and near the top of the engine

Both the deaer tank and radiator cap outlets join under the plastic overflow reservoir

Replaced the heater valve with a new onc from City Racer, and there are approximately 70 hose clamps connecting that, the return, the engine and all of the adapters and elbows.

The original cable was rusted solid, but the choke cable was still good and not going to be used, so I shortened it and did some switcherooing.
Nov 16, 2010
Second fill up this weekend. 240 miles on the odometer, plus about 25 that happened before I figured out how to make the odometer work. Tank took 12 gallons.
265/12 = 22 mpg. So that's cool, especially considering I was warming it up for 10 minutes twice a day to drive 10 miles to work and back.

The Great Wiring Adventure, starting with my pet octopus:

I did not intend to rewire a bunch, as long as the original wires were good I was perfectly willing to live and let live and integrate the new engine into them.
But they weren't good.
In the pre-project test driving, ground problems and broken wires popped up for everything, there were a bunch of extra wires for an emissions computer that wasn't there and wouldn't be replaced, and all of the connectors were ready to explode into dust when touched.
So I resolved to rewire the whole thing.
It took about a month of designing it all, and then about three months of constructing the pet octopus relay box, replacing connectors on all the lights, laying out and taping up the wire harness from front to back.
I found different colored wire loom on Amazon that was pretty easy to figure out and order, so I took advantage of that to try to make things a little easier if I need to look at a problem in the future.
Wires in black loom are associated with the Cummins engine harness.
Yellow loom is lights, controls, and basically anything that is "The Land Cruiser"
Blue is Dakota Digital sensors and controls
Red is for hot battery cables
This worked pretty good until the end, when I would want a small chunk of a certain size and only had wrong colors available. So it's not perfect.

Since I started from scratch, almost none of the original Toyota colors mattered. I started with some sort of established standards and then made it up from there.
Trailers: Brown=tail marker, yellow=left, green=right, white=ground, reverse=purple, and trailer brakes=blue. Honestly, I don't know if that's a real standard or just what the first picture on google says.
Red=hot right now, black=hot when the ignition is on
That leaves orange for brake lights, and then it started to get ugly.

Finding wire with stripes is a little hard, and then there are usually 100 foot minimums. Using a 3 foot section of a color once is ok for Toyota, because 10,000 Land Cruisers are going to use 6 miles of wire, but I don't want 97 feet left over.
I used Corsa Technic for a bunch of connectors, and found that they have some striped wire available in some sizes, but it would have cost about $400 just to do the windshield wipers.

Then a coworker came up with the epiphany of using different colored heat shrink at each of a wire and I was off to the races.
With 11 easy wire colors and 10 easy stripe colors I didn't have to use anything twice.

This counts as something I would do again, but I would use those last three wire colors available and have less stripes, because those were a little tedious.

Rewiring everything was also an opportunity to do some things I wanted that might have been difficult otherwise, like have a headlight warning buzzer, not run all of the current for everything through a 50 year old ignition switch, and put some cooler reverse lights in
Nov 16, 2010
Shortened the interior Cummins wire harness in a few places, mostly the warning wires, and OBD reader and the tach. According to the Youtube videos you're not supposed to shorten the throttle pedal wires, and the Murphy gauge is on the far left of the dash so I didn't need to touch it.

This hole where wires went through originally happens to be the right size for the coupler, and the engine side harness can reach it even with the computer on the left fender

Warning light panel and Murphy Gauges

The logic that led me to make the warning light panel instead of just using the Dakota lights available was not quite perfect, and I probably wouldn't do it again, but the hole is already cut so there's no going back.
Cummins says: Need two warning lights, one yellow one red. Dakota only has one light, it's red.
Cummins warning light inputs are a ground connection: you send 12v constant to the light, the Cummins wire completes the circuit by setting to ground when needed. Dakota box wants 12v only when the light is on. Could have gotten around that with a relay, but would still have the not enough lights problem.
Same with the Wait To Start light, that would have been easy enough to connect the Dakota to the grid heater solenoid though.
I kind of wanted a big green 4wd light like Dad's Land Cruiser had when I was in Kindergarten.
Need a place to put the Dakota button anyway.
All of that led to: Make a panel
I was going for the 1984 FJ40 rare silver dash look, but then completely forgot to paint it silver before assembling it, and didn't feel like disassembling it.
That yellow check engine light that I put a lot of effort into having? Yeah, it's always on and I covered it in tape the first time I wanted to drive in the dark.


What I would do next time, is put the Murphy Gauge on the right (like I've seen in almost every other build because it's a good idea) and a small hole for the button on the left.
Maybe two holes, one for the dimmer knob which is in the old choke cable hole now.

On to stuff that is working out, the LED reverse lights are really nice, and there are no extra switches to run them.

This relay is set up so that when the headlights are off, the original reverse lights are used. "Hey, just letting you know I'm backing up, don't want to blind you or anything"
When the headlights are on (taillights actually, so turning just the running lights on will do the trick) the reverse light power is routed to the LEDs.

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