??? throttle cam return spring??? only "spring" i know of is tha big one between throttle arm and timing arm.. has nothing ta do with "cam"?
part number of you're lookin' at....
all parts sites i've got show invalid part number??? but is it half moon kinda shaped large spring that has a "tang" on both ends?.. if so tha tangs go in two holes.. onein tha block and one in tha throttle arm assem.. its installed when complete timing/throttle arm is installed with tha 3/8" bolt....
looking at your drawing.. tha 90* tang on tha right fits a 1/8" hole in tha block..tha 90* tang on tha left fits a 1/8" hole in tha arm assembly. (lower or throttle part) it has to be installed as tha complete (both pieces) throttle, timing arm is installed with tha 3/8" bolt.... it pre-loads tha assembly ta keep pressure towards idle, against 1/4" idle stop screw....