When our camry needed a new short block the rattle got worse with heat soak. The noise wasn't that loud, worst on slow summer urban cruises with the windows down. It sounded normal under full throttle and had plenty of power. Could only hear it at slower speeds below 35-40 under acceleration.

Took the dealer a while to diagnose but I knew it was the bottom end the whole time. Bottom line if it's a rattle inside the crank case good luck.