Hope this is a relative quickie, and much appreciate the assistance

Help with Timing question;
Here goes, a little background, 496 stroker , blower setup, BM 250 blower and chiller; flat top -3cc as I recall, Teague recommended stage 2 blower cam( very similar to 525 I believe, cam set straight up, with 5* ground in) Degreed cam w/ wheel, all good, matches card, MSD ignition and dist. Lightest weights and springs.

originally set up timing up at approx 28-32, open, on engine stand! think it liked lower end of that scale: (ran really good and set carb) Holley 1150 dominator w/ adjustable mains-( I know yuk) however did install afr’s both tailpipes, so I static set timing WITH 0 degees , with rotor on #1 slightly advanced!

ok without any more delays, As I was starting last couple times, was getting kickback, so slowly retarded dist until it cranked and fired up, all good other than being cold, warmed up engine mostly, checked timing;

Here is the strange part, I get like 10-15 Degrees retarded on the timing light, also seems to run a little rugged, so now as I advance timing and she starts running smoother, and recheck at full open timing, now only shows approx 5* advance @ 3/4 throttle

nextime I start it again kickback! Again I retard, start it, warm up, advance and runs good again, rinse and repeat every time, I have double and triple checked my TDC on #1, of compression stroke( which I I don’t think is the issue, is it possible I have the dist off one tooth or 180*. Knowing the #1 wire lines up! Eagerly seeking help with any/all possibilities needing to be checked.

TU all, for your time

open the distributor and make sure it is not rusted up and stuck and full advance. common problem with MSD. I wont even run their stuff anymore with all the ones I have replaced.

This ^^^^