After doing a serious amount of reading here and on the "other" website I decided to change the radiator cap on my 57 with original V8 position radiator and heater core. Had been running a Gates # 31517 15-18 lb. cap with a safety vent lever. Decided did not want to take the chance with blowing the heater core with the resulting mess and hassle. Switched to a Stant # 10328 7 lb. cap which also has the safety lever. Weather has not been very co-operative in getting the 57 out to see how the temp gauge does after the switch.