Hello all,

So I just picked up a 98 z28 m6 with 90k on her. Once the motor gets nice and warm I have a pretty bad knocking noise from 2k rpm to 3500 rpm and then it sounds like a sewing machine at idle. There is no power delay and the thing purrs like a kitten until she gets nice and warm. The motor is bone stock internally. The noise sounds to be on the driver side or under the intake mani. I have searched a bunch of forums and have not found a pin point solution. I don't think it's a spun rod bearing or atleast hope not. I am hoping to get some constructive input before i start ordering parts and tearing this thing apart. Any and all input is much appreciated!

 

Any Ideas?

 

Ls1's are notorious for being knocky/clacky on a cold start. As far as being warm when it does this I have no idea.

I dont think it is a rod bearing. As far as I remember if it was, the noise would increase with rpms and it would sound like a deisel at idle.

 

Thats what I hear, this is my 2nd LS1 and I cant isolate the noise, pulled the valve covers off yesterday and everything looks and feels solid, a friend thinks its a rod bearing but I have great Oil Pressure, massive power and no metal in the oil. It seems to be passenger side almost next to the intake manifold, maybe a push rod? Just bought the car Saturday and Iam not looking forward to a rebuild already. lol