Help?

First time posting, my son has a 400EX with a 440 kit and a Keihin FCR carb. After riding it for a period of time it sat in his mom’s garage for several years. He asked if I could revive it and I thought, how hard could it be? I found leaky valves so I removed the head and had a fresh valve job done. Upon reassembling it I realized it has an aftermarket cam. (Hot Cams) with EHR 8 inscribed between lobes. I have tried to time it using the stock timing instructions but to no avail. I cannot find any numbers to determine age. In hind sight I wish I had made note of the timing marks prior to disassembling
. My question is, would anyone know if I use the factory timing set up or does it require advancement at the cam gear?