If you buy used cam, you don't know how the previous owner done to the cam. Did he properly break-in the cam which is the most important to performance/life of the cam. Did he used the correct cam break in lube, etc? This is not some item like ECU that they won't wear out, camshaft do wear out and is very critical that follow the proper camshaft break in procedure. I hope you get your money back and just go get yourself a set of new cam and save yourself some time.