Like the title states i have a 2001 durango with a knocking sound coming from the engine. Originally the engine had a missfire on cylinder number 5 and found it to be a cracked exhaust valve, with that replaced and the engine back together it runs much better but still has a similar knocking sound. Just curious if anyone has had issues with knocking sounds from the 4.7l engine, if so what the culprits have been.

Thanks

 

If a piece of the valve broke off, it could have crushed the ring groove of the piston, which means the ring is effectively peened in place and the piston will slap from side to side. It will be a knock, lighter than bottom end (rod/crank), but much deeper than valve clatter.

Did you see any dings along the edges of the piston when the head was off?

 

Didn't notice any dings around the edges... if i remember correctly there were a few dings in the center of the piston, but nothing near the edge. I did check the rod bearings and wrist pins which seemed to be fine, so that doesn't leave much else it could be. Looks like i will be taking the cylinder head off again.

 

It's a bummer, man. I went through this a couple years back on an S-10 blazer. Did an intake gasket and started it up. All was well for a few minutes, then it stopped cold. On restart, it had a miss and a knock. Leakdown test showed #3 exhaust valve was damaged. I yanked the head and replaced the valve, then put it all back together. Miss was gone, noise wan't. Ripped the head back off and sent it out to see if there was anything wrong. Nada. I was left with no choice but to yank the piston. Low and behold, a tiny depression had smashed the ring groove. So I ended up putting 6 new pistons in the truck and lost 2 days on a $700 ticket. Really sucked.

I now make damn sure that nothing got blown/kicked/etc. into the air tube. I was always so careful with the ports and manifold, but just grabbed the air tube and tossed it on. Something had been stuck in the corrugated part and finally got loose and went down the hole. Never did find the culprit.