If you’ve read out articles on the 6.0L Powerstroke and the 6.4L Powerstroke and how terribly both of those engines are, you might get the impression that I hate Navistar International. Sure, they were responsible for building two of the worst modern diesel engines ever to be used in trucks like the F250, but they also have a long history of building commercial engines, with one of those being the DT466.
So, in this article, we’re going to take a deep dive into the International DT466 and what makes it so special and such a legend in the world of trucks. We’ll look at the good, the bad, and everything in between. Let’s get into it.
Where it all Started
To get this whole thing started, we need to rewind the clock to 1967, which is when the development of the International Harvester 300 and 400 series began. Back then, International had multiple divisions, one of them being the Construction Equipment Division, and that division had its own engine division, which was a little awkward because International had its own engine division based out of Indianapolis.
With that in mind, the VP of the Construction Equipment division, Bill Wallace, was the one who actually wanted a new line of in-house engines that were fully designed and built by International. Reportedly, it was a big uphill battle, but Bill eventually convinced them to develop a new line of engines by taking the idea higher up, as basically all the International Divisions at that time needed an engine upgrade, so what better time to develop a line of engines to cover multiple divisions of the company?
With that in mind, that’s how we ended up with the 300 and 400 engine series. They share the same basic structure and architecture, a lot of the same parts, and they were built on the same tooling and assembly lines. What makes these engine lines so interesting is that they both have engines with different displacements and power levels within the 300 and 400 series, but both engine series have their own shared bore sizing.
What I mean by this is that all 300 series engines have a bore of 3.875″ and all 400 series engines have a bore of 4.30″ bore, with the largest 400 series engine coming in with a 5.35″ stroke, which is the DT466.
Tractors and Construction Equipment
Fast forward to 1971 and the initial plan was for the entire 300 line, the 414, and the 436 to be used mainly in the AG division, tractors, and combines. The DT466, on the other hand, was supposed to be used mostly in construction equipment. Soon that changed, but let’s not get ahead of ourselves here.
The 414 and 436 found immediate homes in the International tractor lines. The D414 debuted in the 1971 966 tractor, the DT414 debuted in the 1066, and the DT436 appeared in the 1466 and the 4166 four-wheel-drive tractors. It wasn’t until 1973 that the DT466 appeared in the 4366 four-wheel-drive tractor. All of these tractor engines had a history of excellent service and usability in the International Investor tractors, and even a little past that when the AG side of International Harvester was sold off and became Case International Harvester.
Unfortunately, the aforementioned engines used by the AG Division didn’t draw in all that much attention outside of the tractor world, as the naturally aspirated versions really didn’t have much to offer beyond just simple tractors. This is when the DT466 was let loose to more than just tractors.
Taking on the Medium Duty Truck Market
After a very expensive tooling investment to the tune of around $500,000, the DT466 was now available to the truck market and it became an option for the Fleetstar, then the Cargostar, the Paystar, and last the Loadstar. All of these received the DT466 between January 1975 and the summer of 1976. As compared to some of the other engines available on these platforms such as the D150, D170, and D190, the DT466 offered significantly more power, better fuel economy, more reliability, and best of all, it could easily be completely rebuilt in chassis, removing the need to fully remove the engine for a rebuild.
At that time, the medium-duty truck market had been evolving towards diesel engines, but the perfect engine hadn’t really been offered yet. Sure, International had a few engines for this market, including the D301, D358, DV462, DV550, and others. Other companies like Perkins, Cat, Cummins, and Detroit Diesel were also in this space, and don’t get me wrong, they had some great engines in their own right, but International was about to completely take the market by storm with the DT466, which quickly became the engine to beat in the medium-duty market.
The original DT466 for trucks was built in 1977 and featured the AMBAC Model 100 rotary pump, but when the DT466B popped up shortly after the introduction of the original engine, the original then became the DT466A. Throughout the years there were a ton of different changes to the DT466 with multiple power figures throughout.
Although there were lots of changes, the easiest way to break it down is with the four generations of this engine, including the DT466A and B from 1971 to 1981, the DT466C from 1982 to 1992, the DT466P from 1993 to 1995, and the DT466E from 1995 to 2016.
Through the half-century run of this engine, many aspects actually stayed the same, including the super beefy, super heavy cast iron deep-skirt block. The crankcase itself weighs a ridiculous 400lbs with massive bulkhead sections and main bearing surfaces. Interestingly enough, something that did changes throughout the years was the bore and stroke.
Earlier versions of the DT466 used a 4.3″ bore and 5.35″ stroke, while the later engines used a 4.59″ bore and 4.68″ stroke. We also see this kind of trend with pretty much all modern engines using a closer bore to stroke ratio for a variety of reasons.
One of the features that made this engine unique as compared to other medium-duty engines of the time, is the use of wet sleeve cylinder liners. These ductile-iron liners gave the DT466 a level of durability and serviceability that hadn’t previously been seen on a medium-duty engine, instead wet sleeves were typically reserved for class 8 engines or even larger.
Because each bore uses its own sleeve, the engine is repairable in the case the piston explodes and damages the cylinder, or anything else damages the cylinder. This makes the in-frame rebuild process even easier, which was one of the initial draws to this engine in the first place thanks to its inline-six configuration.
Inside the engine, you’ll find a massive, 150lb forged steel crankshaft with induction-hardened journals for improved wear resistance. The crank is bolted into place by seven main bearings, which got bigger as the DT466 changed throughout the years. Bolted to that beefy crankshaft, you’ll find equally beefy connecting rods.
Depending on the version of the engine you’re talking about, you can see the OEM connecting rods hold up to over 1500hp, which again, shows how beefy and overbuilt this engine is, especially considering the factory power output is around 1/7th of that 1500hp figure.
On top of the block, we have another massive component, which is the cylinder head, weighing in at a ridiculous 250lbs. Depending on the version of the engine, you’ll find either 2-valves or 4-valves. Both versions feature ductile-iron rocker arms, hardened valve seats, and six bolts per cylinder. That being said, the biggest weak point of the DT466 is actually found here, with the OEM head bolts being the weak link of the entire engine.
That being said, you generally won’t see any head or head gasket issues until you’re north of 1000hp.
The oldest versions of the DT466 come in around 1400lbs when fully dressed and dry, with the modern versions weighing even more thanks to emissions control systems, with some models tipping the scales at over 1900 lbs.
And really, that’s the overarching theme of the DT466 as a whole, it’s insanely heavy, typically a few hundred lbs heavier than similar engines from International’s competitors, while also being very underpowered. While that’s not great for performance, it’s great for reliability and keeping the engine in one piece when you creep over four-figure power numbers.
Throughout its 45-year run, this engine saw tons of changes, from mechanical injection to electronic injection, non-intercooled to intercooled, and emissions-free to emissions-plagued. That being said, it always used direct injection, turbocharging, a strong and heavy-duty block, and simple architecture.
With that in mind, let’s quickly hop into each generation so I can explain what makes each one unique, starting with the DT466B.
This variant was rather obviously very similar to the DT466A, as they came out at similar times and really are just subvariants of each other. One of the changes to the B engine was a revised ring pack to reduce oil consumption as compared to the A engine. The compression ratio was also increased from 15.5:1 to 16.3:1 to help bump up the power a bit, which is one of the overarching themes with the DT466 as a whole, is that it’s pretty underpowered.
The B engine also received wider main and rod bearings were also added. We then eventually saw another subvariant appear, which was the DTI466B, with the I standing for intercooled. Both the DT466B and the DTI466B both used the aforementioned AMBAC 100 injection pump and they had power ratings ranging from 160hp up to 210hp.
Fast-forwarding up to 1982 and the DT466C was introduced, and they had made a number of improvements, including larger lifters, an improved oiling system, and changing the injection pump to the Bosche MW. There was a turbocharged version of this engine and two intercooled turbocharged versions. The air-to-air intercooled model was known as the DTA466C and the air-to-water model was known as the DTI466C.
By 1987, the DTA466C produced 240hp and 609lb-ft of torque. To help keep that new increased power figure cool, the water pump was upgraded as compared to the earlier engines.
That takes us up to 1993 when the DT466 yet again went under a transformation following a few years of development. This time around it was designated as the DT466PLN, which stood for Pump Line Nozzle. There was also an “NGD” in the name, which stood for New Generation Diesel. Really, a lot of this was kind of some marketing ploys, as the engine was still mechanically injected, however, that was soon to change.
The NGD PLN engines had a high-mounted pump and a cast squared-off valve cover with notches for the injectors. They used either a Bosch P3000 or P7100 injection pump. Depending on who you ask, this is considered to be the best DT466 ever, as the Bosch P7100 pump flowed significantly more than previous injection pumps, which means that it’s much easier to crank up the fueling and ultimately crank up the power.
This version of the DT466 was rated at 275hp and 800 lb-ft, which is still underpowered given the engine’s size, but definitely a step in the right direction.
But unfortunately, as the story of pretty much every diesel engine goes, the EPA began to enforce stricter standards that required cleaner diesel engines, and so the International joined forces with Caterpillar in the mid-90s to develop Hydraulic Electric Unit Injectors, also known as HEUI.
As a result of their development of this new electric injector came the DT466E, which was introduced in May of 1995, and along with this electronic injection system came a new cylinder head. The bottom end featured all the same upgrades that we saw on the DT466P. Power for the new DT466E ranges from 195hp up to 250hp, with late Maxx Force engines reaching 300hp and higher.
Unfortunately, the introduction of the electronic injection system was really the downfall of the DT466, as it was incredibly reliable before, but never reached that kind of reliability again with the electronic injection system. That system is known for being problematic and having a ton of little failing points that can cause the engine to not run entirely.
Ironically, the rest of the engine is still just as good as ever. That strong and reliable base is still there, but the electronics draped on top of it cause problems.
So, that’s the legendary story of the DT466 from International. Like I said at the start, a lot of people like to clown on the Navistar International name for their complete and utter failures with the 6.0L and 6.4L Powerstroke, but those engines are rare examples of when everything goes wrong with a design. The DT466, on the other hand, represents what diesels used to be and could still be today without all the electronics and emissions systems mandated by the EPA.
The DT466 completely changed the medium-duty truck market and set the bar. It’s crazy reliable, dead simple, and super hard to break. In fact, they’re so reliable, so simply, and so hard to break, that these engines are actually the engine of choice n the world of high-performance tractor pulling, where we see some extreme examples outputting as much as 4000hp at 300lbs of boost. Of course, those engines aren’t stock, but it shows you just how good of an engine the DT466 is. When I say it’s a diesel legend, I mean it.
International produced more than 2 million of these engines between 1971 and 2016 and they can be found in everything from box trucks to school buses to farm tractors to construction equipment.
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