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Old 09-22-2019, 09:06 PM   #1
Bobbed72
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Rod knock?

Afternoon/Evening all, Got what I am fairly certain is rod knock on a rebuilt 5.3. Started after taking the truck to the drag strip. Ran fine for the year prior.

Problem starts after about 5-10 minutes of driving. Goes away when I let off the gas. I notice the motor is fully warmed up long before the noise starts and the oil pressure remains between 30-40.

Researched the great web in hopes of finding something other than actual rod knock being the problem. Pulled the pan and checked the pickup tube oring (should of looked at the rods while I was at it). Didn't see any glitter in the oil pan.

Checked the flexplate cause I heard that they could crack. Solid.

Checked the rockers for anything loose. All good.

Considered detonation. My AFR's look good overall but I'm only monitoring the left side of the motor. Reduced my timing (engine is carbed) across the board by a few degrees and the noise is all but eliminated. Is there anything that could of made detonation suddenly a problem? or are the lower cylinder pressures reducing the knocking force?
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Old 09-22-2019, 10:13 PM   #2
BigBird05
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Re: Rod knock?

Check the internet on your roller lifters.
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Old 09-23-2019, 10:38 PM   #3
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Re: Rod knock?

First thing I considered but I don't know why reducing my timing would make a lifter stop ticking.
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Old 09-27-2019, 06:25 PM   #4
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Re: Rod knock?

Quote:
Originally Posted by BigBird05 View Post
Check the internet on your roller lifters.
Pulled the manifold and the valley cover to check the lifters. Could only see half of them. Pulled the valve covers and checked the rockers and turned the crank to see if everything moved ok. It all looked good.

I did notice when I pulled the manifold off many of the gaskets were disintegrating and several of them had big chunks missing. Replaced all the gaskets and put it all back together and so far no knock. Thinking it was detonation.
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Old 09-28-2019, 11:54 PM   #5
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Re: Rod knock?

Do you have a cam? Do you have stock rockers? If so I'd check the rockers again to see if the caps are walking out of the rockers. If they walk out completely its gonna be a bad day.
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Old 09-29-2019, 08:20 AM   #6
Bobbed72
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Re: Rod knock?

I heard about that, so I rebuilt the rockers too with a kit that adds c-clips to the trunnions to keep the caps in place.

Just a mild cam in it. LS1 cam.
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