Chrysler Slant-6 engine
Chrysler Slant-Six was the promotional name for an overhead valve inline-6 engine produced by Chrysler Motors between 1959 and 1991, and it remains in use as a popular reference name for the powerplant. Featuring a reverse-flow cylinder head and cylinder bank inclined at a 30-degree angle from vertical, it was introduced in and displacements for the 1960 model year. It was a clean-sheet design known within Chrysler as the G-engine, built as a direct replacement for the flathead Chrysler straight six with which the company started business in 1925.
The design proved very successful, being utilized in cars, trucks, boats, and agricultural and industrial applications.
Naming
The Slant Six nomenclature did not emerge as an auto-enthusiasts’ nickname. Though the phrase isn’t seen in 1960- or 1961-model Valiant brochures, it was used in Chrysler’s own press releases and advertising concurrent with the Valiant’s late-October 1959 introduction and initial production year.Design
The Chrysler Slant Six engine was a clean-sheet design, led by Willem Weertman, later Chrysler's chief engine designer. Its characteristic 30° inclined cylinder block gave it a lower height, copying the same cant Mercedes-Benz had introduced in 1952 in its M186-engined 300SL sports car. This enabled Chrysler stylists to lower hood lines, and also made room for the water pump to be mounted with a lateral offset, significantly shortening the engine's overall length. The slanted cylinder block also provides space in the vehicle's engine bay 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 No. 1 and No. 6 intake runners are of approximately equal length, the No. 2 and No. 5 equal but shorter, and the No. 3 and No. 4 equal and shortest. This has the effect of broadening the torque curve for better performance. The Slant Six manifold configuration gives relatively even distribution of fuel mixture to all cylinders, and presents less flow restriction. This, in turn, provides 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.It was introduced in two displacements in 1960: The "LG" in the compact Valiant, and the "RG" 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. The G-engine was used by Chrysler's international operations in locally produced vehicles. It was also 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 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 2G 5-bearing Hemi, and fewer mains results in a crankshaft better able to withstand the effects of torque. Efficient cooling and lubrication systems, a favorable ratio of connecting rod length to stroke, and a forged steel crankshaft all contributed to the engine's strength and durability.
The G-engine was designed for utility and economy, and gave better overall performance than its competitors at its 1960 introduction. It generally kept up through the 1960s and early-1970s with its direct competition, though specialty 6-cylinder engines like the Pontiac OHC Six, a brief GM outlier designed for its sporty Firebird pony car, bested the performance of most versions of the Slant-6. After an early factory racing program was discontinued by 1962, the Slant Six did not receive much performance development. Most Slant Sixes 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-wheel-drive cars. A new V6 engine was created for the 1987 Dodge Dakota compact pickup truck by removing two cylinders from the corporate LA V8 engine. It replaced the Slant-6 in the rest of the Dodge truck line at the end of the 1987 model year.
Significant production changes
- The combustion chamber shape was slightly modified for 1967 to promote more complete combustion and reduce exhaust emission toxicity.
- All G engines used forged steel crankshafts until the middle of model year 1976, when a less costly cast-iron crankshaft was introduced. The cast crankshaft uses a different block, different main and connecting rod bearings and different connecting rods.
- The counterbore in the rear flange of the crankshaft was diameter until 1967. For 1968, it was enlarged to. This difference has implications when swapping engines with automatic transmissions.
- All G-engines used solid valve lifters through the 1980 model year, with the exception of a small production test of hydraulic lifters in the 1978 model year. For model year 1981, all North American G-engines received top-fed hydraulic lifters. Retrofitment in both directions is possible.
- Emission control devices and systems, carburetor make and specification, and engine assembly details changed over the years to comply with market requirements and preferences.
- Electronic ignition, which had been made available on V8 engines late in 1971, was made standard equipment on all engines including the RG in 1973.
- Induction-hardened exhaust valve seats and upgraded exhaust valves were made standard in 1973 to withstand prolonged operation on no-lead fuel.
Configuration variants
170
The 170 engine was offered in model years 1960 through 1969 in North America, and through 1971 for export markets. The first vehicle to offer the 170 slant-6 was the 1960 Valiant. The engine has a bore of and a stroke of for an actual displacement of. Connecting rod length is. The "LG" low-deck block was unique to the 170 engine.198
The 198 was introduced in the North American market for model year 1970 as a more powerful base-model engine than the previous 170 engine. The increased displacement gave improved vehicle performance and lower manufacturing cost, for it was achieved with the tall RG block also used with the 225 engine by installing a crankshaft with stroke and connecting rods long, for an actual displacement of. Manufacturing costs were reduced by eliminating using two different blocks for the two different available sizes of slant-6 engine. The 198 engine was available through the 1974 model year.225
The 225 used the RG block with a bore, a stroke and connecting rods, for an actual displacement of. This undersquare geometry was a departure from the emerging trend towards oversquare engines. It provided strong low-rpm torque characteristics for automobiles and trucks, as well as other commercial and marine applications. The 225 was originally designed and introduced in 1960 for use in full-size models, and it eventually became the best known of the Slant Six engines. The original Chrysler 225 Slant Six produced around at 4,000 rpm and of torque at 2,800 rpm.In 1982, Chrysler signed an agreement with Perkins Engines to build a dieselized version of the 3.7, with seven main bearings and turbocharged as well as naturally aspirated in Windsor, Ontario. Design work had started in 1975, but with the collapse of the diesel market in North America, these plans were cancelled in 1983.
Aluminum block 225
Between late model year 1961 and early model year 1963, approximately 52,000 die-cast aluminum RG blocks were produced and installed in passenger cars. These open-deck blocks used integrally cast high-nickel iron cylinder liners, and bolt-in iron upper and lower main bearing caps. Internal components were the same as used in the iron engine, and an iron cylinder head was used with a special copper-asbestos gasket. The aluminum block weighs about less than the iron RG block.Although serviceable examples can still be found, the aluminum RG tended to undergo delamination between the iron cylinder liner and the surrounding aluminum. Severe corrosion within the block is also commonly found because of the general tendency in the 1960s and 1970s to fill cooling systems in summer with plain water without corrosion inhibitors. Moreover, the open-deck design and primitive head gasket technology are not sufficiently robust to withstand the increased seal demands of increased compression or forced induction.