If it knocks when it is warm. If it does it cold that could be the notorious "Piston Slap" problem with the LS engines. This goes away as the engine builds temperature.
Knocking Sound?
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
Knocking Sound?
I've been chasing this a bit, but maybe someone here has seen this issue before.
I have a fairly loud, metallic sounding knock coming from somewhere down low on the front half of the car. The sound increases with rpm and is loudest under light load between 2k-3k rpms. The sound isn't bad on cold start, but gets worse after the car has been running a minute or so.
I've put my hands all over the headers, but can't find any obvious points where the headers touch something solid. I hope this isn't anything engine related, but most importantly I just want to understand the issue.
Thanks in advance!
I have a fairly loud, metallic sounding knock coming from somewhere down low on the front half of the car. The sound increases with rpm and is loudest under light load between 2k-3k rpms. The sound isn't bad on cold start, but gets worse after the car has been running a minute or so.
I've put my hands all over the headers, but can't find any obvious points where the headers touch something solid. I hope this isn't anything engine related, but most importantly I just want to understand the issue.
Thanks in advance!
Last edited by BQuicksilver; Aug 18, 2008 at 12:45 AM.
Drifting
Joined: Aug 2008
Posts: 1,491
Likes: 1
From: Goldsboro NC
I've been chasing this a bit, but maybe someone here has seen this issue before.
I have a fairly loud, metallic sounding knock coming from somewhere down low on the front half of the car. The sound increases with rpm and is loudest under light load between 2k-3k rpms.
I've put my hands all over the headers, but can't find any obvious points where the headers touch something solid. I hope this isn't anything engine related, but most importantly I just want to understand the issue.
Thanks in advance!
I have a fairly loud, metallic sounding knock coming from somewhere down low on the front half of the car. The sound increases with rpm and is loudest under light load between 2k-3k rpms.
I've put my hands all over the headers, but can't find any obvious points where the headers touch something solid. I hope this isn't anything engine related, but most importantly I just want to understand the issue.
Thanks in advance!
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
Sweet. 
Is there any way I can tell rod knock from a bad lifter or pushrod issue?
BTW: The sound isn't bad on cold start, but gets worse after the car has been running a minute or so.
Is there any way I can tell rod knock from a bad lifter or pushrod issue?
BTW: The sound isn't bad on cold start, but gets worse after the car has been running a minute or so.
Thread Starter
Safety Car
Joined: Dec 2001
Posts: 4,295
Likes: 2
From: Indianapolis Indiana
Cruise-In III Veteran
Cruise-In IV Veteran
It doesn't sound like this, but from reading the thread where I pulled this the video might be a badly bent pushrod. I assume rod knock sounds different?
http://media.putfile.com/LS1-knocking
It doesn't sound like this either.
http://media.putfile.com/0718081435
It DOES sound like this, esp when under the car.
http://s255.photobucket.com/albums/h...t=100_1502.flv
http://media.putfile.com/LS1-knocking
It doesn't sound like this either.
http://media.putfile.com/0718081435
It DOES sound like this, esp when under the car.
http://s255.photobucket.com/albums/h...t=100_1502.flv
Last edited by BQuicksilver; Aug 18, 2008 at 01:03 AM.
Drifting
Joined: Aug 2008
Posts: 1,491
Likes: 1
From: Goldsboro NC
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Racer
Joined: Mar 2007
Posts: 401
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From: Down in the west Texas town of El Paso TX
Get a mechanics stethescope. They really help isolate noises. If you don't have one a real long screwdriver will work if you hold your ear to the plastic end after you place it where you think the noise is. I found a knocking
fuel pump on my 68 El Camino that way.
fuel pump on my 68 El Camino that way.
