Why want the rod bearing cap tighten down own your 98 Pontiac grand prix 3.8 l it has new bearings?
Sounds like you have the wrong bearing shells.
The 1996 Pontiac Grand Am is a front wheel drive application. This vehicle has sealed (non-serviceable) and bolt-in wheel/hub bearing units. Removing and replacing them involves removing the wheels/tires, brake rotors and then unbolting the wheel/hub bearings. The General Motors OE front hubs are AC Delco #2025K.
I had a 1998 GP which is almost identical in every respect to your 2003. The front driver's side bearing went bad and the dealer charged me about $500 total for the repair. I wanted to do it myself but the bearing is actually an entire assembly, not the inner/outer roller bearings held in with a simple snap ring like older cars. The part alone was about $200, so I figured saving my knuckles was…
The front wheels bearings are sealed in an assembly. You cannot replace the bearings, just the entire assembly. I priced out the units about 5 years ago and I was quoted anywhere from $150 to $225 each. I asked the parts suppliers if replacing them is a DIY job and most advised against trying it myself.