Base model engine certified 27 July 1942. 125 hp (93 kW) at 2450 rpm, 6.25:1 compression ratio, dry weight 244 lb (111 kg)[1]
O-290-A
Certified 27 July 1942. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 251 lb (114 kg) with SR4L-8 or N-8 magnetos, 245 lb (111 kg) with N-20 or N-21 magnetos.[1]
O-290-AP
Certified 21 July 1944. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 251 lb (114 kg) with SR4L-8 or N-8 magnetos, 245 lb (111 kg) with N-20 or N-21 magnetos.[1]
O-290-B
Certified 22 January 1943. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 247 lb (112 kg).[1]
O-290-C
Certified 22 January 1943. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 238 lb (108 kg).[1]
O-290-CP
Certified 21 July 1944. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 238 lb (108 kg).[1]
O-290-D
Certified 13 December 1949. 125 hp (93 kW) at 2600 rpm continuous, 130 hp (97 kW) at 2800 rpm for 5 minutes, 6.5:1 compression ratio, dry weight 230 lb (104 kg).[1]
O-290-D2
Certified 1 May 1952. 135 hp (101 kW) at 2600 rpm continuous, 140 hp (104 kW) at 2800 rpm for 5 minutes, 7.5:1 compression ratio, dry weight 233 lb (106 kg).[1]
O-290-D2A
Certified 20 April 1953. 135 hp (101 kW) at 2600 rpm continuous, 140 hp (104 kW) at 2800 rpm for 5 minutes, 7.5:1 compression ratio, dry weight 236 lb (107 kg).[1]
O-290-D2B
Certified 30 September 1954. 135 hp (101 kW) at 2600 rpm continuous, 140 hp (104 kW) at 2800 rpm for 5 minutes, 7.0:1 compression ratio, dry weight 236 lb (107 kg).[1]
O-290-D2C
Certified 8 May 1961. 135 hp (101 kW) at 2600 rpm continuous, 140 hp (104 kW) at 2800 rpm for 5 minutes, 7.0:1 compression ratio, dry weight 235 lb (107 kg).[1]