i recently picked up a 2007 Suburban with the 5.3L engine notorious for AFM problems. It’s got a loud tick (see video linked below) and cylinder 8 is misfiring even after replacing plugs, wires, and injectors. That’s not one of the AFM cylinders though. Could the lifter have gone bad? It was my impression that the non-AFM lifters never really go bad. I assume it is possible that the cam lobe is flattened as well but if that’s the case then the lifter almost certainly is trashed too, right?

Part of me wants to do a full engine flush or driving it for a few hundred miles with Seafoam in the crankcase to see if the lifter (if that is the problem) will unstick but I’m afraid of doing that and causing more damage than is already there.

 

Does it "dog" on acceleration? Sounds like something is hitting something. At that rpm, I don't think it's a lifter

 

When you say “dog” you mean if it seems like it has no *****? I haven’t driven it in over a week so I don’t remember. I have to drive it tomorrow so I’ll pay attention for that. I’ll also take another video when it’s warmed up if that’ll help.

 

Yep, no get in go. The rpm that I hear on you video is too fast to be a lifter. I replaced a cam shaft on my 82 350 due to a cam lobe rounded off. It didn't have any get up when I punched the accelerator, just a bump.

 

What did your old 350 sound like with a rounded off cam lobe? Anything like what mine sounds like?
I have also wondered if maybe that noise is rod knock but I think it’s also too fast to be that as well.

 

I didn't make any noise, just wouldn't accerelate

 

Can you isolate the sound to one side of motor? What rpm was video? Last oil change - any metal in pan?

 

 

Here is an updated video at idle after being warmed up. I didn’t notice any lack of ***** when leaving from a stop either.

 

It does sound like a lifter, however as you increase the rpm, I don't hear the noise follow it.