Ford el inline 6 tensioner

Hi iv rebuild my el engine after a head gasket replacement but I’m stuck on the tensioner and retainer part. The retainer is unusually tight to screw pack into it’s flush state but the problem for me is with the allen key iv got the right one but it just won’t nudge in any direction to lock it and my retainer isn’t screwed flush bc of it and I’m stuck can someone recommend anything please