Mickey
Saw what yours is doing on other thread, mine is a
400 pontiac
Timing pretty much the same

Timed mine today, after installing timing tape,
Initial 28 deg
Total 52 deg

Starts right up, idles real lopy
Does not like to idle under 800-850
If you try it will idle until you rev it up and it comes down and dies
950...very stable doesn't die coming down off revs

Might have to kick your idle up

Followed a thread today that said 280 cams need 900-1000 rpm to stabilize

I have a 4 speed man so don't have any load at a stop like you would