I have a 1977; with a 1968 327/HEI...the car has been an ongoing project for several years. I've recently been driving it more and found that it would overheat after about 15 minutes, someone on the forum suggested I check the timing--so, now my problem:

I rubber banded the centrifugal weights, disconnected the vac adv and plugged it, and hooked up the timing light. At a low idle, I then dialed up the gun until the timing mark on the balancer reached zero. The dial read 42 deg!!!! That is 42 deg with no advance at all. This can't be right... what am I doing wrong? I have the gun hooked to the #1 plug wire, and the power is coming from the alternator electrode.

I figured that the timing was way off (although the car ran fine, just overheated), so I proceeded to adjust it. I set the gun to 12 deg, and turned the dist clockwise (about 15'ish deg) until the timing mark on the balancer read zero. In order for the car to not die, I had to increase the idle on the carb several times. With this setting, I then removed the rubber bands to check the timing at idle, which was the same (so the weights are good so far)... Let me note here that I observed a bit of unburned fuel smell with this setting. I then set 36 deg on the gun and had my teenager run the rpm up to 3000...the balancer mark moved from below and up to the zero mark - all adv appeared to be in at 3000. I thought i was good to go...during the road test, it completely bogs down when I stomp on...virtually no power at all...HELP. What am I missing??

Did you ever figure this out?

do you have vacuum advance still operational and did you disconnect it before adjusting timing?

Make sure your harmonic balancer hasn't slipped.
I like to take a compresson gauge, remove the schader valve & possibly remove the gauge itself, put it into #1 , place thumb over the hose end, turn engine over by hand til you feel comp. coming out. When it stops, you should be close to TDC #1, check mark on balancer & rotor at #1 wire at the dist.