The P-63A was powered by an Allison V-1710-93 engine rated as follows:
Takeoff: 1,325 hp
WEP (dry): 1,500 hp
WEP (wet): 1,820 hp
Note that the P-63 was a very fast climber, exceeding 4,200 fpm below 10,000 feet in WEP (dry), and even better when using water injection. Climb to 10k was about 2 minutes, 20 seconds. Its roll rate was very fast 110 degrees/sec at 260 mph. The P-63 had a laminar flow wing design of considerable area. Pilots stated that it would easily out-turn a P-51B. One pilot stated that "head to head with P-63, a P-51 had virtually no chance."
What prevented the P-63 from seeing front line service with the USAAF was its lack of range. This was not a problem for the Soviets, who liked the P-63A very much.