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 (tall) 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