Verifying TDC on a dampner (timing chain slack)

I want to verify an old 340 dampner is accurate. I have a piston stop installed and the dampner stopped at 6 degrees BTDC when rotating clockwize and at 7.5 degrees ATDC when rotating counterclockwise, I know the chain has slack backward so do I call this good. I really want to rig a dial indicator into the holetobe certain. The timing chain and gears are new

turn crank till the dampener slit is at 15 BTDC. install stop till it firmly contacts the piston. turn crank CCW till the piston contacts the stop. if the slit is at 15 ATDC then the slit is dead on. I would also measure how much slack the chain has & measureing that at the dist rotor will also include dist intergear/lower tang slop combined with the chain slop. Check by turning the dampener CCW carefully till the marks are at 15 BTDC (keep the chain taut in that direction) then turn the crank back CW till a helper hollers that the rotor JUST moves (use the dial indicator for that). that distance on the dampener in degrees is that total slop amt

Any slop in the timing chain would have absolutely no bearing on the damper markings to TDC.

Sounds like you need to adjust your pointer or the mark on you damper.

Your looking at the dampener only, not the camshaft Maybe the outer ring has slipped some If so replace it now before it slides all the way off

Bill is absolutely correct there (I had to delete some of my post material)/was thinking of two things at once!. You would need to start further back than 6 deg cuz you're into or close to being into the piston dwell area when you're that close to TDC

Oh dang, I'm a dummy.
Fresh from recently degreeing a cam and checking lift etc I didnt even snap. I simply had a senior moment (early LOL) THANKS guys