how many valve springs per Valve ? 273 hp

hi, the 273 came with a single spring only!! no doubles or dampners!! the 340 spring was the first to use a dampner.the specs on 273 is 100# seat, 184 # open. the comp cams spring 901 is better spring for 273 , 101# seat, 242# open. just food forthought. the dampner was to control valve float.