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Just finished rebuilding this forge rods/piston engine due to warped HG surface. Ran "fine" before but it was overheating/blew HG. decided to swap the bearings as there was some scratches on there. Checked clearance and torque to spec.
Primed the engine but since i put new rings and honed the cylinder decided to do a break in. Completed high idle till warm then proceed to drive with increasing load.
Got back after ~ 20 minutes of driving and started to hear this knock or tap?
Saw some air bubble on the oil so I thought maybe oil pump gasket was bad and thought maybe air was getting to the lifter(thought oil held pressure). Decided to put all new pump + gasket instead. Recheck push rod length(stock heads) and even tried a longer pushrod that increased preload from .063 to ~.095 (currently have the LS7 summitracing lifter in).
Rechecked my rocker arms (i just did the che trunnion) but swap to stock and still the same.
At this point im thinking its either rod knock or collapsed lifter?
All the lifter are pretty hard when I try to push by hand and took a video with valve cover off and they are all moving.
Before I spend more money and buy lifters, HG and do all this work I figured I'd get some opinions if thats even a possibility.
Only thing that I noticed is under 2000rpm or low idle its pretty loud. When I rev 2000+ it seems to go away? I think i can MAYBE still slightly hear it, not sure as the engine is decently loud. I was thinking if its rod knock it would be louder?
I also already tried disconnecting each cylinder and didnt make a difference.
I’ll be the odd ball in the group, and say it’s potentially a rod bearing. I completely rebuilt my Lq4 earlier this year. I developed almost an identical noise. I thought it was a lifter too. Tried 2 different sets of pushrods thinking it was lifter preload. It made the noise from idle to 2000 rpm’s, and then quieted down above 2k rpm’s. After about 500 miles I started hearing a raspy noise at high rpm that I thought was detonation. It kept getting louder. So I pulled the engine and it was 100% a rod bearing spun.
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Is this Knock or Lifter 
