chamber heads are 321, 322, or 323 depending on year. The only difference between small and large chamber Gen-3 heads is the combustion chamber size. The advertised power drop from the 1971 ratings to the ones for the 1972 model years (for example, the 1971 304 produced 210 hp and the 1972 304 was 150 hp) is not due to any engine changes, but an industry-wide shift from SAE Gross (also known as "brake horsepower" or "bhp") to SAE Net power ratings. The 1971 and 1972 engines produce the same power. The 1971 and earlier versions were rated using "gross" horsepower, which is with the engines operating with no accessories or drive belts, air filters, nor any exhaust system restrictions. The change to the more realistic "net" horsepower ratings for 1972 and later required the engine to be driving all stock factory accessories and to use the factory air filter system and a simulated factory exhaust. Power is measured at the flywheel for both systems. For example, even with the modifications to reduce emissions and increase efficiency, AMC's engine was among the strongest factory-spec engines available in an American car in 1971, with more horsepower than Pontiac's standard and Chevrolet's that powered the Corvette. 304 The 304 has a displacement of , which produced (gross rating) in 1970-71 and was built starting in 1970. Output declined yearly thereafter, initially due a shift from SAE Gross to SAE Net horsepower. 1972-75 models were rated at (net rating from 1972 onwards). It was rated at in 1978, and in 1979, the last year it was installed in passenger cars, and in 1980–81, the last years it was used in Jeep vehicles. The International Harvester Corporation SV "Comanche" V8 engines are sometimes mistaken for the AMC 304, however, the IHC V8 engine family has no relation to the AMC V8 and was in fact first produced in 1959, 11 years prior to the AMC designed 304. The similarity in displacement is purely a coincidence. 360 The AMC 360 has a displacement of . The 2-barrel produced to in 1970 to early 1971 while the 4-barrel produced to , to from mid-1971 through 1975, to in 1976, in 1977, and from 1978 through 1991. This engine was used in the 1970 AMX as the base engine and also in the 1970 Rebel, the 1971 through 1978 Matador, Jeep J-series trucks from 1970 until 1987,