my engine makes a thunking noise.... not all the time just when its warmed up. it gets worse as i drive. its somewhere in the lower end and ive ruled out the harmonic balancer and fornt seal.... plz help ask anything you need to know

 

Could you elaborate on this thunking noise? Is it consistent? does it vary with RPM? is it only present under load (when the throttle is pressed)?

 

Bearing going out?

I have an 88 IROC with the LB9. My original engine had a factory defect in the bottom end, and when it had about 25k miles on it, it developed a bearing knock. You could only hear it after it warmed up and the oil thinned. I took the car back to the dealer since it was still under warranty, and they put in a new short block. The new bottom end has been quiet for over 100k miles.

 

I agree. A little more detail would be needed to determine where you should look. A broken tranny mount is just one of the many potential problems. Does the car still run okay besides the clunk?

 

yeah any questions that i can answer may help...it seems worse at low rpms ie louder, i cant feel it more( in the throttle pedal... i have solid engine mounts), its only after warm up and sometimes when i crank over, it seems to come only while cruising and idle not so much under power, it sounds like thick metal to thunk metal... actually say thud and thats pretty close. the car still runs fine and strong. i didnt notice the sound or feel it b4 i took out my smog pump( to take it out i had to rerout the belt and get a longer one). the thunk definite ly varys with rpm too...... its most present at idle( 1000 according to my tach), and seems to ge down in gear( 800 rpm), and is nearly indetectable at any higher rpms.

 

i hope its not a bearing... well im prolly gunna pick up the 403 that is in my other thread Engine swap questions..... if i do ill rebuild this one and tell yall what it was..... WE WILL HAVE CLOSURE!!!!