There's a locking clip on the front of the Cam that holds the gear in place. If it breaks or wears away, the Camshaft tens to push on the Welsh plug at the rear of the block that is an oil seal. That plug is up against the Bell housing
Post in thread 'How not to build the 2F' How not to build...
The Physics of sound...
Things like this can be very tricky because vibrations (like electrons) will travel through the path of least resistance and the bellhousing may be acting like a diaphragm in a speaker, or like two tin cans with taunt string between them like a childhood walkie-talkie...
If sound is increasing when you're on the Bellhousing, it seems like sound is traveling through the block. BGarcia beat me to it, but I too would check the valve train, particularly the lifter/pushrods before tearing anything apart.
FWIW, if/when you get to that point of replacing the Pilot...
I've never removed one with the flywheel still on, so I don't know how tight the cap is in there, but "should" be able to wiggle it out....
Someone who has done this should chime it at this point.
That's an very odd sound for a end bearing to make, but I suppose it's possible. They call it a 'Rod Knock' for a reason 'cuz there's a rod involved with the ignition thrust.
Can you carefully put the stethoscope rod on one or the other of the rod cap bolts while the engine is running?
Isn't...
If you don't get a noticeable diminishing of the knock when pulling plug wires (when the wire on the offending cylinder is pulled), it's not a bottom end issue.
You're gonna need an automotive stethoscope or something of than nature to isolate the approximate location of the sound.