My brother and i were listening to a noise my 289 has been making, and we think it is a main banging around. It is a very low deep knock, and is very hard to hear. But after running the car down the road and back and letting it sit at idle, you cant hear the noise anymore. Any chance it is the pin that connects the rod n piston together?

 

Get you a stethoscope and you will be able to here were the noise is coming from

 

i have one, where should i place it to figure out if it is a main or not?