for the past 2 days everytime i drive my car i hear some hitting noise sound under engine bay(the noise is constant it keeps going as the car is idling) . if the car is on parked or nuetral it sounds loud. on drive not as much. my main bearings are going out. (seen metal parts on oil from oil change.) but the power is still their. so im thinking it could be the flywheel. i have hard starts thats why im thinking and hoping its the flywheel making this sound. any ideas??

 

Heh you're hoping it's anything but bearings

How much metal in the oil - a few sparkles, tons like a metal thickshake, or actual chunks?

What's the 'smack' sound - dull like bits of 4 x 2 banging together? Definitely coming from the bottom end? A rod bearing knock is exactly rhythmic and loudest at idle; bad main I've never had but understand they are pretty much silent until they seize.

Pull spark leads to disable cylinders one at a time, see if you can get it to stop.

 

yes like 2x4 smacking together, on the oil its more like metal thickshake and Definitely from the bottom end. i went under. iether the block or flywheel. its a 91 z28 l98. and no loss of power at all