Are rods supposed to be loose?

you really shouldnt be able to move them all that much...especially if they are torqued down. there is a tiny gap in between each rod and each main cap...but i dont think you would be able to notice it by moving it with your hand

If I remember correctly, I don't think there should be anymore than o.o20" of play between the rods. Get a feeler gauge and measure.

And make sure all your rod bolts are torqued correctly and no bearings have been spun.

Scratch that. If you have the engine pulled and have a knock, take it apart and look at your bearings. Leave your pistons in unless you want to buy new rings and re-hone your cylinder.

Also check your crank-end play. Should be .004-.008".

ARP specs. Rod bolts- 28 ft-lbs
Main bolts- 65 ft-lbs

If you have a bunch of miles on the factory shortblock, piston slap could be possible.