Knocking/Tapping.

[heptofite]

Once i get my B2 warmed up it tends to knock very faintly at idle, not quite the same sound as a lifter, and nowhere near as loud as a lifter.

a few weeks back i accidently double-gasketed an oil filter and blew all my oil out on the ground, engine was running maybe two minutes without oil before i figured out why i had no pressure, but oil pressure is good right now.

Could my mains be going out?

if they are, how long could i keep this engine alive in that case, and how big of a pain is it to replace them?

 

[Big Jim M]

If you are in doubt about the sound then it is almost always a top end noise. Rods and mains leave little doubt about where the sound is coming from. If you really ran it completely out of oil the top end would complain loudly as the pressure went away. This usually causes the driver to turn the engine OFF before permanent damage is done.
I'd forget about it and wait and see if the noise gets worse and worse.. Which I doubt from your post.
Big JIm

 

[heptofite]

well, the lifters sound a different pitch than this new sound, the new sounds is a deeper note.

also, the other day, i punched it from a light and then took my foot out of it almost immediately and the strangest sound i've ever heard came from under the transmission hump, it was kind of like a cellphone vibrating against a wood floor, except about ten times louder, and it didn't go away untill i manually shifted it into neutral.

 

[Big Jim M]

That could be u-joint noise..
Big JIm

 

[heptofite]

it does it when i'm stationary.

 

[IMenriched]

it does it when i'm stationary.

Might be a torque converter showing signs of age.
cracked/loose flywheel/flexplate
loose /worn engine mount or tranny mount
loose /worn starter
loose exhaust...cracked exhaust manifold.
or as you fear something interanal

could be something simple like ice build up...if you are in northern climate.