LC9 pushrod/rocker issues and an embarrassing mistake.
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Teching In
Joined: May 2019
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LC9 pushrod/rocker issues and an embarrassing mistake. I'm sorry if I'm in the wrong place. I know its an LC9 which is technically not an LS but you guys seem to know these engines well. About 6 months ago I installed a texas speed DOD/AFM delete into my 07 LC9 5.3 in an avalanche. I also installed new cam gears and a new LS7 chain tensioner because the stock tensioner had exploded sending plastic everywhere. This caused a whole lot of very bad noises that i originally thought was a stuck lifter. I also installed a new chain because the original chain was WAY loose. Anyways, over the last few months ive noticed a louder and louder cold knock. Now its to the point where i can still hear it when its warm but its not as loud. Sounds to me like valve train. Now for the embarrassing part...When i pulled the pushrods out I put them all in solvent to clean them. I never labeled them. I guess i thought that with hydraulic lifters that pushrod length didnt matter to the point that I needed to keep them matched to the rocker. Did I make a huge mistake here? If i were to replace the pushrods...what length do i need? I've read anywhere from 7.385 to 7.400??? Should i put a trunnion kit in also? Which one?
TECH Senior Member
Joined: Jun 2016
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From: Central Cal.
The LC9 IS an LS engine.
The OEM pushrods are all the same length, nominally 7.4". Matching them is not a concern.
Get to the bottom of the noise, get a good book on overhauling the LS, and have at it.
The OEM pushrods are all the same length, nominally 7.4". Matching them is not a concern.
Get to the bottom of the noise, get a good book on overhauling the LS, and have at it.
Thread Starter
Teching In
Joined: May 2019
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How much effect does preload have on knocking. If my preload is out of spec but not to the point of being loose, will that cause a knock. I guess i just dont know if i need to tear the valve covers off and check pushrod length with a tool or if i can just order 7.4" pushrods and use them. Everything i read sais they are 7.385 from the factory. I put a LM7 cam in it when i did the DOD AFM delete but i thought that all the stock parts should work with it?
Top end noise is usually described as ticking not knocking. Cold knock is sometimes piston slap.
On stock lifters, moving your pushrods to different valves is highly unlikely to affect anything. If your preload moves say .025, that can be a problem. Stock lifters are usually varying by .005.
How is your oil pressure?
On stock lifters, moving your pushrods to different valves is highly unlikely to affect anything. If your preload moves say .025, that can be a problem. Stock lifters are usually varying by .005.
How is your oil pressure?
Thread Starter
Teching In
Joined: May 2019
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Top end noise is usually described as ticking not knocking. Cold knock is sometimes piston slap.
On stock lifters, moving your pushrods to different valves is highly unlikely to affect anything. If your preload moves say .025, that can be a problem. Stock lifters are usually varying by .005.
How is your oil pressure?
On stock lifters, moving your pushrods to different valves is highly unlikely to affect anything. If your preload moves say .025, that can be a problem. Stock lifters are usually varying by .005.
How is your oil pressure?
Oil pressure is at the lowest 15 psi. That is fully warm. When its ticking, its 40 psi plus because it's cold. I run standard 5w-30.
Warm idle at 15 combined with the sound you are describing makes me think rod knock and spun bearing. I hate to say it but I think you are in for a tear down.
The pushrods thing did not cause it. Debris in your oil may have from the tensioner going out
The pushrods thing did not cause it. Debris in your oil may have from the tensioner going out
