A newly rebuilt engine will probably use a little oil, how many miles did you run to use a 1/2 qt. - 1.0 qt.? Was the exhaust smokey? Radiator cap pressure will depend on what has been replaced in the cooling system, new modern radiator and heater core? The 250 engine could run 8 - 14 psi but the rest of the cooling system may not be able to stand that pressure.

1957 Chevrolet 5700 LCF 283 SM420 2 speed rear, 1955 IH 300U T/A, 1978 Corvette 350 auto, 1978 Yamaha DT175, 1999 Harley Davidson Softail Fat Boy