Hello All, I am putting together a 305, I did not tear it apart, replaced the intake mf, carb, dizzy, ripped out the smog and emission crap out of a 87 firebird. dialing it in, but I hear a bad sound at idle,, rev it goes away,, idle back down,, bad noise. almost like a socket in the upper end bouncing off the rods.. (NO there is NOT a socket in there) any thoughts???

 

Does that happen with all the belt drives removed?

 

I did not try that,, ill have to get the belts off and fire it up, wont be running long though with the water pump disconnected. long enough though to see. I was thinking rod knock,, like i said throttle up and it goes away, but on idle sounds like a socket bouncing around in the intake cavity.

 

You might have a lifter struggling to "pump up" at idle and one of your rockers is slapping the top of your valve, but when you rev it up then the lifter pumps up and brings that rocker back into adjustment. Just a thought....