I have a 72 small block 350 Corvette motor that had a basic engine rebuild. Stock pistons, stock heads, stock cam. The only mods are a streetmaster manifold, holley 600 and I put a Hei distributor on it. I timed the motor to 8 degree btdc and it seems I have hesitation on my take offs , but at about 3500 to 4000 she really takes off. I had the timing way off like 14 btdc and it seemed to run better. I shot the timing and plugged the vacuum advance when I shot the timing and plugged the hose to carb. I'd like my acceleration off the line to be more responsive. Any suggestions or advice or insults appreciated.
You need to confirm your timing marks with a piston stop test , your light is telling you stories . Balancer rings move and there's quite a few different cover, pointer, and balancer configurations Or time it by ear and seat of the pants and forget the light
Assuming you trust your timing marks, I'd plug the vacuum advance and set the initial at about 16-deg BTDC... then hook up the advance and see what the curve looks like thru the RPMs. Kill it and see how easily it restarts. Drive it and see if pings under load (too much adv). You also have a choice between hooking the vac advance to full manifold or ported vacuum... the only difference being whether you see static or vac advanced timing at idle. Many folks call for no more than 36-deg total advance, and to have it all in by 2500 or so... but I just went with what felt right after LOTS of driving and tweaking.