I'm trying to swap calipers on my car and having trouble getting the new ones installed. There is a tab on the pad that is supposed to line up with the slot circled in the picture but it's rotated on an angle a bit. I can get the tab in and the circlip attached but as soon as I go to try and set the caliper itself pad pops out.

Is there a way to rotate the piston with out dismantling it and damaging it, or should i just return the caliper? Compared to the old one it doesn't seem to be put together correctly.

Its the right rear btw

 

It's not a brake caliper from a 3rd gen Camaro or Firebird.

Sorry for my mistake. I forgot about the 88 down Delco-Moraine rear brake calipers. Actually trying to forget about them because they absolutely suck.

 

Those pistons rotate in the bore with either the specific tool for that or any other method you can figure out.

Those 82-88 rear calipers are such a pain to deal with.

 

^ I've been able to turn them with a large enough channel locks. Be careful not to snag the rubber