American Motors also changed the AMX's engine lineup for 1970 with the introduction of a new 360 cu in (5.9 L) four-barrel (290 hp (220 kW), P-code) to replace the 343 cu in (5.6 L) V8. The smallest 290 was dropped and AMC could claim 65 more base horsepower than the AMXs had previously. The 390 cu in (6.4 L) V8 engine continued, but upgraded to new heads with 51 cc (3.1 cu in) combustion chambers that increased power to 325 hp (330 PS; 242 kW) at 4800 rpm and 430 lb⋅ft (583 N⋅m) of torque at 3200 rpm.[72][73] The code remained "X" for the engine on the vehicle identification number (VIN).