In this day and age, engine technology has reached an incredibly advanced stage, the likes of which were unthinkable even just a couple of decades ago. Innovations such as Koenigsegg’s proposed Freevalve valvetrain technology come to mind, along with Porsche’s recently-patented direct start tech for use in mass-market vehicles. EVen as the wheels of time turn, there seems to be no end in sight to what engineers and designers can come up with to improve the automobile engine as we know it.
However, one glaring aspect of all of these proposed engine advancements is the relative loss of durability and ease of repair that was seen in several engines of yesteryear. Take the Chrysler Slant-Six, for example. It was one of the most reliable and long-lasting engines of the 20th century. It wasn’t built to dominate racetracks or show ther world the very edge of possible advancement; its job was to get whatever vehicle it was installed in from point A to point B as reliably and trouble-free as possible.
Diagonally Mounted, Positively Dependable
Chrysler Slant-Six Key Points
- Production began in 1959
- Debuted in the 1960 Dodge Dart and the 1960 Plymouth Valiant
- Mounted at a 30-degree angle in the engine bay
- Production ceased in 2000
Before the introduction of the Chrysler Slant-Six in 1959, The Detroit giant had been using the Chrysler Straight-Six engine, which had been in production since the company’s founding in 1925. Suffice to say, by 1959, it was time for a change. To kick the project off, Chrysler top brass selected an engineer by the name of Willem Weertman to head up the project to replace the aging Chrysler Straight-Six engine.
Even back then, the slant-six engine design was nothing new. Mercedes-Benz had been using this type of configuration since 1952 in the 300SL. The reason for using an engine with a cocked angle was two-fold. First is the issue of packaging. A slanted inline engine has a lower overall installed height, meaning the vehicles it’s fitted to can have a lower hood profile, leading to sleeker styling and a lower center of gravity. It also allows for a more compact under-hood package, requiring less engine-bay space required.
Chrysler Slant Six Engine Diagram DrawingWikimedia Commons: Moebiusuibeom-en
There’s also the slant engine’s performance benefits to point out, too. Because an engine mounted at an angle changes the geometry of most everything else under the hood, this means its intake/exhaust manifold needs to be altered, as well. In the Chrysler Slant-Six’s case, its intake runners, or the individual tubes in its intake manifold, change in length over a conventionally-mounted engine. Because of this, the Slant-Six is able to have a broader power band over other engines of similar size and with a similar cylinder count. Its broader power band allowed the Slant-Six to be ahead of the curve regarding other six-cylinder engines throughout the 1960s and early 1970s.
Everything Changes With Time, Except The Slant-Six
While the Slant-Six debuted in 1959 for the 1960 model year, changes began to take place immediately. For example, in 1961, Chrysler began offering both cast-iron and aluminum-block versions of the slant-six, with the aluminum version being more oriented towards performance. The aluminum-block slant-six, carrying the engine code RG, was produced until 1963 due to owners quickly falling victim to something called delamination between the RG’s iron-sleeved cylinder liners and the surrounding aluminum block bores. Aluminum engine construction was still in its infancy back then.
A few major changes took place throughout the remainder of the Slant-Six’s life. The first of which occurred in 1967, when Chrysler modified the Slant-Six’s combustion chamber to promote a cleaner air/fuel mixture burn. Overall, the motor wasn’t subject to many changes over the course of its life. As they say: “If it ain’t broke, don’t fix it.” We’ll take a look at the rest of the Slant-Six’s changes seen throughout its life below:
- The Crankshaft counterbore was enlarged from 1.25 inches in 1967 to 1.50 inches from 1968
- Electronic ignition was made standard in 1973
- The introduction of unleaded fuel in 1973 led to Chrysler modifying the Slant-Six’s exhaust valve seats to increase their hardness
- Switched from forged to cast-steel crankshafts in 1976, resulting in the motor requiring changes to its block, main bearings, connecting rods, and connecting-rod bearings
- Solid lifters were swapped out for hydraulic lifters following the 1980 model year
1964 Plymouth Valiant Chrysler 3.7L Slant-Six EngineBring A Trailer
In total, there are three size variations of the Chrysler Slant-Six. The smallest iteration measured at 170 cubic inches (2.8L) and was in production from 1959 to 1969. Next in line was the 198-CID version (3.2L), which lasted from 1959 to 1974. Topping the range was the 225-CID, or 3.7-liter. The 225-CID variant was the most popular, and was the only one to last throughout the Slant-Six’s entire lifespan, which lasted until 1987 USDM light trucks. However, the Slant-Six’s production would continue through the 1991 model year for marine applications, and until 2000 as a crate engine.
It Was Exceedingly Reliable
1961 Chrysler Slant Six Engine on Engine StandWikimedia Commons: Greg Gjerdingen
As with many inline-six cylinder engines like Ford’s gigantic 300-CID (4.9L) mill, the Chrysler Slant-Six was an extremely reliable unit. One of the hallmarks of the Slant-Six’s reliability was its use of something called a deep-skirt design, which means its crankshaft is mounted above the oil pan rails, leading to better structural durability and integrity. Along with that, the Slant-Six uses a four-bolt main bearing setup identical to the one used on the second-gen Chrysler Hemi-head V8.
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We also can’t forget about the benefits of its forged steel crankshaft. The process of forging simply put is carving a crankshaft out of a block of steel, rather than pouring liquid steel into a mold, or casting a crankshaft out of the same material. Its cooling and oil system were also robust, meaning the Slant-Six could be put through heavy use for long periods of time without suffering any sort of lubrication issues or overheating.
Its overall simplicity of design also helped it achieve its reliable nature. Because the motors were small and usually installed in engine bays designed to also be used by larger V8 engines, it was extremely easy for laypeople to work on the Slant-Six. Parts were, and still are, cheap, as well, meaning anyone who needs to repair a Slant-Six can without having several specialized tools or deep pockets.
Could The Slant-Six Ever Really Be Replaced?
The Slant-Six was discontinued in 2000, 13 years after it was no longer offered as an engine choice in Dodge’s light truck line. Unlike other old motors which were phased out due to emissions incompatibilities or outdated designs, the only thing that stopped the Slant-Six from continued use was its size. As Chrysler was transitioning to front-wheel drive platforms, the Slant-Six was deemed too long for use in a transverse setting. So, the decision was made to ax it, and Chrysler’s 239-CID (3.9L) V6 replaced it.
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It can be argued that the recently-introduced Hurricane straight-six is the Slant’s spiritual successor. First seen in the 2022 Jeep Grand Wagoneer, the Hurricane is now seeing use in Ram 1500 pickup trucks and the new Dodge Charger. It has a 3.0-liter displacement, and with the use of two turbochargers, it can produce up to 550 horsepower. Along with being the Slant-Six’s spiritual successor, the Hurricane motor is meant to replace the Chrysler/Stellantis Hemi V8, much to the despair of American gearheads everywhere.
Sources: Chrysler, Stellantis, Dodge, Ram, EngineLabs.com.
