Hi guys,
I'm working on finishing up a 5.3 swap into my 88 1500. The engine came from a wrecked 01 suburban. It runs and drives great but the engine is making a faint knocking noise. The noise can only be heard at idle and is faint enough I can only hear it outside the truck or when next to another vehicle or wall with my windows down. Although it's not loud it seems to me to be to deep to be a loose rocker arm. The truck has 35lbs oil pressure at hot idle so I don't think it is a main bearing. I was told to unplug each coil individually to test if it was a Rod and that the noise would go away when I unplugged the knocking cyl but the noise never changed. I know there are a million threads on piston slap on these engines but I wouldn't think it could be that because it's worse when hot than when cold. At cold start you can barely hear it. Listening under the truck. But what's weird is that I recently took a 100 mile trip in it and when I got to where I was going the engine was perfectly silent with no noise at all but then when started the next day it was back. If you guys think it's a lifter can use I don't mind pulling the heads and doing s cam swap with new lifters, pushrods, and springs but I would hate to drop the money to do that on a bad engine. Also I just changed the oil and it appeared clean with no metal particles at all. This is currently my daily driver and only vehicle so I'm trying to figure out what the issue is before treating it apart so I can have all the parts on hand to get it done in a weekend. Any help would be greatly appreciated.
Thanks guys!

Here is a video:

 

I couldnt hear anything in the video that stood out in my eyes.

But if anything, it sounds like every other 5.3 out there with a maybe a little lifter tick. I wouldnt be concerned at all with the sound it makes, the 258K mile 5.3 in my old sierra made lots of lifter noise and it never skipped a beat.

Just add some trans fluid the oil, maybe like half a quart and run it for a oil change and see if it helps clean the lifters up. Otherwise I'd just continue to romp on it and drive it without a worry.

 

Thanks for the reply. It's not as easy to hear in the video as in person. If you standing beside the truck it's enough for someone to ask why it's knocking.

 

It was the oil pump oring. Had good oil pressure but must have been sucking air bubbles. Was a heavy knocking noise. Changed the oring and all noise is gone!