i have a 97 LT1 with 104k miles. the motor has never been rebuilt. sometimes when i start it it will knock about 5 to 10 times then run fine. it doesnt usually do it when its cold..it does it when the motor is hot and has been turned off for 30 minutes or longer. i think it could be a main bearing going but i wanted to know for sure before i pulled the motor

 

A spun bearing will knock all the time. Maybe a sticky lifter?

 

i dont know...its a heavier knock rather than a tick