I see this two ways------either your balancer mark is actually wrong, or regardless of how many times you've degreed the cam, you are doing something wrong.
A borescope is no way to check timing marks. Get/ make yourself a piston stop. This is mine I've had since the 70's. This is for a small block so just an example
View attachment 1715767469
if you buy one make sure you figure a way to lock the plunger as some are poorly designed and can wiggle/ move
You are not trying to stop the piston "at TDC" but rather some distance down the bore
To use, disconnect bat, remove no1 plug and make sure piston is down some. Screw in the stop and carefully wrench the engine over. Pulling all plugs makes this easier. When the piston comes up and is stopped on the device, make a temporary mark onto the balancer directly under the TDC mark on the timing plate. Now do the same going CCW, and when done you will have to marks. The true TDC is halfway between your two marks, and if the OEM is correct that is where it will be
