There are not many of anything that you can call a Legend but the Navistar/International DT466 diesel engine has to fall into that category.
If the 466 is not enduring I don’t know what is. The fact that you can bolt almost any part from a 466 built ’78-’93 or ’94-2004 on to one another is reality and not folk lore. Try that with any other engine manufactured in the last 25 plus years and you have a better chance of lighting striking you down crossing the street.
The Navistar DT engine family is a line of mid-range inline-6 diesel engines (Figure 1). The Legend DT 466 is a four-cycle, six-cylinder engine with 466 cubic inches of displacement. The bore and stroke are 4.59 by 4.68 inches (116.5 by 118.9 mm). The compression ratio is 16.5:1. The maximum power output is 260 horsepower at 1,900 rpm while the maximum torque output is 800 ft-lbs. at 1,400 rpm. The engine uses direct fuel-injection combustion technology and the aspiration system is turbocharged with wastegate technology and an air-to-air intercooled design. The governed engine speed is approximately 2,500 rpm.
With horsepower ratings ranging from 170 hp (130 kW) to 350 hp (260 kW), the Navistar DT engines are used primarily in medium-duty truck and bus applications, although prior to 1986 Navistar International, then known as International, the DT engine was used in farm and construction equipment.
The DT engines are of a wet-sleeve design. This means that the cylinder wall (sleeve) is a separately machined part that fits into upper counter bores for sealing at the top with O-ring housing bores cast into the engine block in the bottom. The cylinder sleeve is in direct contact with the engine coolant, hence the “wet” sleeve. These sleeves are prefinished and do not require honing after installation. They also allow for easy in-frame overhauls during service.
This design is commonplace in larger displacement diesel engines and is considered one that enhances durability because the consistent wall thickness of the sleeve allows for even heat transfer, ensuring the cylinders stay round during thermal expansion. Additionally, it gives the ability to use a hardened cylinder sleeve that is more durable and wear resistant than a softer, cast-in wall. Also, the replaceable cylinder sleeves protect the block from damage (e.g. in case of foreign objects entering the cylinder) and can easily be replaced, which enables simpler restoration to original specifications.
The 466, however, being a high production mid-range diesel, is somewhat unique in its wet-sleeve design, because nearly all the other high production mid-range engines are in-place cylinder blocks. The down side to this scenario from the reman standpoint is that wet sleeve engines will readily have “in-chassis” overhauls – the upside is that over a million of these engines have been produced in the last 25 years, and that is not counting those used in farm and construction applications during the years prior.
The 466 engine is an inline six cylinder wet sleeve block that has six upper counter bores and six lower packing areas where the rubber seal is installed. This is a deep saddle casting where the crankshaft lies completely inside the block. Piston cooling jets bolt into the main oil gallery of the block and spray oil into the bottom side of the piston for cooling of the head of the piston.
Three different blocks were used in the various iterations of the 466. The first block going was used from 1978-1982 and carried casting numbers 675500C1/C2/C3/C4. This block had 1? lifter bores and they were a flat lifter-style.
The second block came on the scene in 1983 and was used through 1987. It carried casting numbers 1802330C1/C2, and had 1.125? lifters – these were a flat lifter-style as well.
The third block, used from 1988-1993, carried casting numbers 1810739C1/1814042C1. This version also had 1.125? lifter bore but used roller lifters and required retainers to keep them from rotating. If needed, this third “roller” block could be backward-compatible to the flat tappet lifter engine with the 1.125? lifter.
Cylinder sleeve protrusion is .0035?± .0015? and can be controlled by shims available in thickness of .002?, .004?, .010?, .020? and .032?. Upper counterbore damage can and may occur with this engine. And when its beyond wear limits it can be sleeved and repaired. The lower O-ring seal area can also be repaired, especially if damaged by cavitation (see Figure 2).
The crankshaft essentially stayed the same throughout the life of the DT466, except that early on the decision was made to increase the main and rod bearing width dimensions. This change, which actually increased the bearing life and dependability, was a judgment call that probably had Rudolf Diesel spinning in his grave.
Engineers reduced the fillet/radius size of both rod and main bearing journals (see Figure 3). Rod journal bearing widths were increased from 1.198? to 1.255? and main journal bearings were increased from 1.219? to 1.296?; the fillet radius dimension was reduced to .192?-.208? for both the rod and main bearing journals. This gutsy move paid off since neither bearing failures nor crankshaft breakage are at all common to this engine.
The connecting rod is forged steel with tongue-and-groove type parting faces as shown in the inset of Figure 4. The forging number of the connecting rod (#688922) stayed the same throughout the engines. This rod is a bit unique in that it always remained a straight piston pin bushing and never went to a tapered top type.
There are three camshafts (Figure 5) that correspond to the three different blocks. The first one is the small 1? flat lifter diameter which pairs with the same lifter bore block. The second camshaft is the 1.25? flat lifter, and the last one is for the roller lifter that is used in the block with the lifter retainers since roller lifters cannot rotate. The flat lifter camshafts can be built up and repaired as shown in Figure 6.
The piston used in the DT466 stayed the same throughout production of the Legend engine. When used in LPG applications the piston is, in fact, made out of the original diesel piston although it has a much larger bowl cut into the head due to reduced compression for the LPG application (see Figure 7).
The 466 cylinder head is a relatively simple two valves-per-cylinder head with a flat deck face and no combustion chamber, since the combustion chamber is in the piston. It has press-in bronze injector tubes and valve recession is .000? to -.020? for both intake and exhaust valves.
Remote outpost areas that may need power or irrigation can drill for natural gas and be able to power a unit almost endlessly. The 466 engine can readily be converted to a LPG or Natural gas application for irrigation and stationary power units where diesel is not readily available. It is one of those engines that does this very well and with less modification in comparison to many others (Figure 8).
The 466 can have the injector tube area machined and you can then install an insert and now install a spark plug where the injector once used to sit.
The Legend engine used three different PLN (Pump Line Nozzle) fuel systems. The first one, Model 100 Ambac, was used from 1972-’82 and looked like the top image in Figure 9. The second pump was a MW Bosch injection pump, used from 1983-’93 and the last one is the PLN NGD pump called P3000 and P7100 used 1994-’97. Their appearances are different enough that there is no mistaking which one is which.
There were three oil pumps in the Legend series of engines. the early agricultural A models used 7/8? wide housing; 1? from 1978-1982 in B models; and 1-1/4? 1983-1993 for C models. For those looking to use the larger pump on the B models, the crank pulley that was made for the 1? oil pump will lock up on the 1-1/4? C oil pump. The B model pulley can be machined to accept a C oil pump as seen in Figure 10.
In Figure 11 you can see the C model oil pressure relief valve: the one on the right is a B series. The additional porting change provided better lubrication to the valve itself.
The Garret T04 series of turbochargers were used on the Legend series 466 engines from 1978-’93. With fixed geometry, the main change in design, other than air ratio control for different horsepower designations, was the turbine housing.
In 1990 it changed from a sleeve-style flange to a Marmon flange (Figure 12). This affected how the exhaust pipe was connected to the turbo and obviously cannot be interchanged without making other major changes to the exhaust system.
Water Pumps, Covers and Thermostat Housings
All truck applications used the eight vane impeller water pump, however there is also a four vane version. The four vane impeller was used only in low horsepower construction and agricultural applications, and will not push enough coolant for 150 horsepower and up Legend engines (see Figure 13).
In 1991 a change was made in the design of the front of the water pump. Up to that point the fan clutch was a stud mount and had the smaller nut that was right hand thread. In 1991 the spin-on fan drive clutch was introduced and used the large nut water pump with left hand thread. The large-nut water pump carries part number 73544C91 and the small-nut water pump is 735327C91 (see Figure 14).
In 1989-’93 the coolant flow was increased in the engine, through its water jackets, as well as the thermostat to front cover transfer hose. The high-flow thermostat housing carries casting number 1813956; the standard from 1978-’88 had 686757C2 (see Figure 15).
The main design of the front cover for truck applications did not change other than in the increased water flow. Agricultural applications used the same casting but the timing pointer is in a different clock position. Combined applications have a wide mount on the bottom and a pre-formed water outlet as opposed to a bolt on water elbow (see Figure 16).
There you have it: the 466 Legend engine. This engine is so versatile that it is found in farm tractors, dozers, fire trucks, and without question is the most popular school bus diesel engine. It’s also in stationary power units and irrigation pumps. In fact, there is no end to where you may find a 466.
My personal favorite is the International CXT, touted as the largest pickup truck in the world. However, in pictures (like the opening photo) may be the only place you’ll see one of these ever again, because International stopped producing these great-looking trucks and seems to have forgotten they ever existed!
I cannot thank the good people of SRC’s Heavy Duty division enough and, in particular, Nick Greer and Jim Thompson, for their hospitality and endless assistance in making this article possible.