There are many threads about this topic, but so far I haven't find an help for what my engine is doing... So I'm asking again.

There is a clack-clack sound that appears in a certain rpm window (2000 - 2500 rpm).

This happens only whith a low load: it disappears in decel and acceleration. It's there only when I keep the speed constant, I have to "aim" at it to make it noticeable.

It's much more noticeable when the engine is cold, once warmed up it's much more difficult to identify it between the other noises.

Without a certain load it's impossible to hear that specific noise, so I have to drive to hear it. At idle I can't spot it, not even using a sthetoscope.

It's not an accessory (I removed the belt).

I disconnected the injectors one by one hoping to identify something, but the noise was always there.

The engine a 98 internally stock LS1 (85'000 miles).
I use a synthetic 0W40 oil.
No misfire, no codes, no KR, Fuel trims around 0%...

What else can I check before I start taking the engine apart?
What could it be?
Rollers? Pushrods? Lifters? Timing chain?

If it was one of those parts I think I would hear the noise at idle... or not necessary?
Any idea?


Thanks

Stefano

 

all three of my motors that spun bearings sounded like a light ticking or tap at that same rpm when you let of the gas. Sounds like the beginning of a rod bearing failure.

 

Is there a way to understand if it's a spun bearing before opening the engine?
This of disconnecting the injectors was an attempt to find that out.
I was thinking that without fuel the cylinder with the problem would sound differently or maybe stop the noise. But no matter which injector I disconnected the sound was there at the same rpm.
By the way: this is a procedure described in the service manual. They just say to disconnect a coil. For me it was easier to disconnect the injectors.