LS2 Engine Knock - Help!
Thread Starter
Teching In
Joined: Aug 2009
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LS2 Engine Knock - Help! I have a swapped LS2 from an 05 GTO. engine hasn't been run too much. After a few startups, I noticed a quiet almost rattle\tick. My first thought was a lifter because the engine has been sitting for some time. It would only tap after warmup, not cold, and only when there seemed to be no load on the engine; for example if its revved up lightly, inbetween the time when the revvs stopped climbing and started to fall, the noise was able to be heard like a floating tap. After a test ride, everything changed. It now knocks with an aweful sound to it, at idle, under load and it seems to be sparratic. It sounds fatal. The idle even sounds a little bit shakey. I'm going to drain the oil next time I am with the car to check for the bronze colored shavings, because I'm thinking now that it's a rod bearing 
I actually took a quick video of it.. not sure how well it captures the sound though.. are we allowed to post utube links on here?
I actually took a quick video of it.. not sure how well it captures the sound though.. are we allowed to post utube links on here?
Thread Starter
Teching In
Joined: Aug 2009
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Staging Lane
Joined: Dec 2006
Posts: 82
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From: Calgary, Alberta
I could hear a bunch of random knocking. Sounded to me like someone was pounding a nail in next to the engine. Later on that sound was gone. If that was the sound, it might be external to the engine. Any engine knock will usually be continuous and rise or fall with PRM.
Thread Starter
Teching In
Joined: Aug 2009
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The sound stays consistsnt with the engine speed. Its hard to tell in the video but if you listen closely you can hear both knocks. One is more in the background while the other is that sparattic almost tick of a knock ( the louder one). It sounds like whatever is knocking sometimes knocks really hard. And thats where the louder knock is. :/
Staging Lane
Joined: Dec 2006
Posts: 82
Likes: 0
From: Calgary, Alberta
For the louder random knocking I would look at possibly something hitting the flywheel or clutch. Or some other outside source. Maybe disconnect the serpentine belt to see if noise goes away. If it is internal to the engine it would be very consistent. If it is internal to the engine something is VERY wrong in there!
Staging Lane
Joined: Dec 2006
Posts: 82
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From: Calgary, Alberta
Keep us posted on what you find. A rod bearing sounds consistent like someone is hammering on the engine from inside. Very mechanical sound. Yours almost sounds like a broken rod swinging around hitting something every once in a while. I doubt that is the case though! I do have a 6 litre truck block that had broken a rod and did no damage to the block! (I bought it like that)
(Also have a 5.3 litre with almost every bearing spun. Castech heads. Probably driven til it wouldn't run anymore)
Hope yours isn't like either of mine!
(Also have a 5.3 litre with almost every bearing spun. Castech heads. Probably driven til it wouldn't run anymore)
Hope yours isn't like either of mine!
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I bought an LS2 from a GTO that the owner swore had a bad main bearing. The car had ~ 28K miles. I tore the motor apart to find a bad lifter that was getting beat up by the cam (the knocking noise), the cam lobe was pretty far gone also.
Thread Starter
Teching In
Joined: Aug 2009
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Im terrible with updating... But it turns out it was a rod bearing after all. My engine must have been abused somehow before it belonged to me -_- most of the other rod bearings had ugly wear on them too. Crank and rod are junk. As or right now the engine is torn down and in the hands of my machine shop. New crank new rod new oil pump bearings and cam bearings going in. Cant wait to put it back together and get some enjoyment out of it
Teching In
Joined: Aug 2012
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From: Bakersfield, Ca
i was hoping it was just a lifter or a bent rod something in top end .....do u recall if u missed a gear right before it started doing that knocking ??? cus thats what happened with me ...missed a gear and 20 mins later i started hearing that noise
TECH Fanatic
Joined: Jan 2010
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From: Euless Tx
If you missed a gear and bounced it off the rev limiter, more than likely it's a bent pushrod. Take off the valve covers and rockers and check them out by rolling them on a flat surface.
