i had my oil dipstick go to the wrong place onetime,it made a pecking noise till i straightened it up i thought i would mention this,you never know,it happened to me
I have a pan mounted dip stick in a 4x4, absolutely a possibility in a car, but not possible in the pan mounted rear sump
Have you tried a different viscosity oil? My 416 makes all kinds of piston noise with 15w40 Rotella. My home-boy hone job is the culprit here, I think. Seems to be getting worse with miles. I'm up to 2500mi now. But I can run 60wt VR1 and it quiets the noise a lot. Might be fun to experiment, Ross.
I also like TomP's rattly header tube hypothesis..... bundle em up with a big hose clamp and see what happens....
So, the noise scares me enough that I don't want to drive it cold, and I have ran 15w40 and 20w50 and a few shelf blends during the times it's been together, so my hunch is the tap I hear is not oil related. Plus all the clearances are blueprinted like every other hot FE I build and been checked "thrice" with the build and reblock and rebuild LOL
As far as the header tube, I will look, but man, it really is a tapping that coincides with engine speed, but I will still look again at the possibility. FYI, there is nothing loose on the truck, I am a bit of a rattle/squeak crazyman.
I've listened to the audio and read this thread thru, thought I could hear it but?. At one point you documented that you verified no exhaust leaks, so this may be old ground and way over-simplifying but could there be a minute crack in a header tube or where they are welded to the flanges? As it heated up it would tend to close and quiet down. Also, a tiny flaw of this type would only manifest under load conditions.
So I have been all over the headers because it often seems logical as a possibility, but it just doesn't sound like that. That being said, this last time I bolted them to a head, no rockers, and pressurized them with air, a whole bunch of nothin with a Windex bottle. Additionally, they are ceramic coated headers that were quiet with the original 396. It all goes back to "new stroker kit came with a new noise"
I have to go out of town for a bit, but hopefully this weekend I can try pulling wires to see if the noise changes. If it does, I would have a head off and a piston out in under 30 minutes