Why advance timing?

Oh, thanks for the pic. Do I need to access that 2nd bolt from underneath?

I drove it about a hundred miles from my mom's house in fairly high outdoor temps a few years ago. No problem. I let it sit for a year and now it seems to overheat and I've just been trying different things for the past couple years. With the advance, it's as close to normal as I've been able to get it.

Judging by the condition of the old radiator, it _may_ have had issues prior to me picking up the car. None of the fins were attached to the tubes, according to my radiator guy. I put the rebuilt engine into it for my mom and she drove it around for about 20k miles, and she had the transmission rebuilt, so the drive train is hopefully in pretty good shape. I've hardly put anything on it in the time I've had it because of the overheating.