Chrysler Slant-6 Engine

Chrysler Slant-6 Engine

The Slant-6, known within Chrysler as the G-engine, is one of Chrysler's better known automobile engines. The engine is an inline-6 piston engine specifically designed such that the cylinders are inclined at a 30-degree angle from vertical. The 30° inclination of the Slant-6 gave a lower height overall engine package, which enabled vehicle stylists to lower hoodlines, and also made room for the water pump to be mounted with a significant lateral offset, significantly shortening the engine's overall length. In addition, the slanted cylinder block provided ample space under the hood for intake and exhaust manifolds with runners of longer and more nearly equal length compared to the rake- or log-style manifolds typical of other inline engines. The Slant-6 manifold configuration gives relatively even distribution of fuel mixture to all cylinders, and presents less flow restriction. This, in turn, makes for relatively good airflow through the engine despite the intake and exhaust ports being on the same side of the head rather than in a crossflow arrangement.

The engine was a clean-sheet design, led by Willem Weertman, later Chrysler's chief engine designer. It was introduced in two piston displacement sizes in 1960: The 170-cubic-inch (2.8-litre) "LG" (Low-G, referring to the relatively short engine block casting and crankshaft stroke) in the Valiant, and the 225-cubic-inch (3.7-litre) "RG" (Raised-G, referring to the relatively tall engine block casting and crankshaft stroke) in full-size Plymouth and Dodge Dart models. In 1960, the engine was called the "30-D Economy Six" engine by Plymouth marketers, referring to the 30° cylinder block angle.

The G-engine was offered in various configurations in the North American market until 1983 in cars, 1987 in trucks, and 1991 for marine, agricultural and industrial use. Replacement engines were still being built in Mexico as of 2000. In addition, the G-engine was used extensively by worldwide Chrysler divisions and subsidiaries in their locally produced vehicles. It was also widely purchased by other original equipment manufacturers for installation in commercial vehicles, agricultural and industrial equipment, and boats.

The G-engine gained a reputation for reliability and durability. The basic engine design is rigid and sturdy, in part because the engine was designed to be made of either iron or aluminum; an aluminum block was produced in 1961-1963, but most blocks were made of iron. The block is of a deep-skirt design, with the crankshaft axis well above the oil pan rails for structural rigidity. Although only four main bearings are used, they are of the same dimensions as those in the Hemi. Efficient cooling and lubrication systems, a favorable ratio of connecting rod length to stroke, and a massive forged steel crankshaft (on engines made through mid-1976) all contributed to the engine's strength.

The G-engine gave better performance than its competitors at its 1960 introduction, and generally kept up through the '60s and early '70s, though engines like the Pontiac OHC Six bested the performance of most versions of the slant-6, and after an early factory racing program was discontinued by 1962, the slant-6 did not receive much performance development; most slant-6s were equipped with a single 1-barrel carburetor. Starting in the early 1970s, primitive emission controls adversely affected driveability and power, though a version of the 2-barrel carburetor package first released for marine and export markets in 1967 was offered in North America from 1977 to 1983 under the "Super Six" name; performance figures were only slightly higher, but driveability was substantially improved. Other Chrysler engines were released with more advanced combustion chambers, electronic fuel injection, and other modern improvements, but the length of the slant six precluded its use in Chrysler's front-drive cars, and a new 3.9 litres (238 cubic inches) V6 engine created by lopping two cylinders off the corporate 318-cubic-inch (5.2-litre) LA V8 engine was devised for use in the new Dodge Dakota compact pickup truck for 1986. The Slant-6 engine was dropped from the rest of the Dodge truck line at the end of the 1987 model year, replaced by the 3.9 V6.