Has anyone played around with one of those adjustable timing chain sets to see if your motor makes any more power by advancing or retarding the camshaft?

With big blocks. My engine and boat and cam liked 4 degrees advanced below 5000 RPM. Intake valve to piston clearance gets close though. I used the Cloyes Hex adjust which wasnt a lot of help since you still had to remove the pump,damper and timing cover to get at it. Id run yours straight up if I were you. Use a good full roller setup and dont trust the manufacturers keys. Dial it in to be sure.

I have a Jesel belt drive system on a Merlin 632. Moving the advance/retard can have some significant effects on where a motor makes its power. My motor picked up about 40HP going from a +4 advance to straight up on the Dyno. That's with a 900HP naturally aspirated set-up @6700 rpms.