Question on pulley bolted to dampner loosening up

First outing with new motor was last weekend.
I have an Innovators West dampner.
Bolted to that i have an aluminum pulley with two grooves. Using the inside groove( closest to block) for the alternator belt. Belt is lined up perfectly.
Anyhow, the bolts loosen up pretty much every pass. Tighten them back up, loose again.
Went and bought lockwashers. Now it will stay tight a couple of passes, then start to loosen up again
Next step( i guess) is to try red loctite, let it setup, and try again.. if that doesnt solve issue, not sure what will.
Ideas?
Btw the motor is balanced, runs well, etc...
Here is a picture..if it helps