Thanks for all the replies
Note, I have not yet tested with alternator and PS belts disconnected. I have also not yet checked the mechanical fuel pump. For oil I am using Rotella 10w-40.
I had some old romex house wire (14-3?). I stripped off the jacket and cut the copper wire into maybe 5" pieces. For each 5" piece, I made a bit finer tip to the wire using a very light touchup with my angle grinder. I dabbed the wire in some di-electric grease and then inserted into HEI cap. I only did 1-3-5-7 as there is minimal (none?) tapping/clicking coming from the passenger side cylinders.
I had the valve covers off. Outside temp was approx. 50 degrees F. A friend had a listening ear that I borrowed. See pics attached. I started the engine and there was some light ticking / tapping. Again, noise coming from driver's side. Just from standing beside engine it again seemed to come more from cylinders 1 and 3. I used the engine ear and the noise seemed to be coming from cylinders 1 and 3. The engine was still on fast idle around 1600 rpm. I had a vacumm gauge attached and the reading was pretty steady around 20-21. I used the test light and started grounding cylinders 1-3-5-7. I could see the spark jumping from the copper wires I had inserted into the HEI cap and the test light tip. It was hard to tell if RPM was dropping - though I could see the reading on vacuum gauge become more erratic. Shorting 1 and 3 seemed to lessen the tapping a bit - though I could still hear it.
After about 10 of the engine running - all of a sudden I started hearing a
more pronouced ticking / tapping and again it seemed to be from cyl 1 and cyl 3. The rpm was perhaps around 1000 at this point. I used the engine ear and it
definitely seemed that the intake on cylinder 1 was clacking. The intake on cylinder 3 seemed to clack - though not as loud as cyl 1. I was not sure if maybe I was just hearing the clacking on intake cyl 3 just because it is right beside cyl 1 intake. Cyl 5 and cyl 7 were making minimal noise and again almost no noise from pass side cylinders. This is video I recorded after around 12-14minutes of the engine idling.
https://youtu.be/uVaps9sGzlA?si=yUQRu9sXGKNX-Dd1
Shorting the 1-3-5-7 showed similar results. I would see the vacuum gauge become more erratic as each cylinder was shorted and tapping seemed to lessen a bit when shorting cyl 1 and cyl 3.
Strangely, after about 17-18 minutes of idling the tapping started to go away. This was video is where the tapping was getting less apparent
and showing the vacuum gauge reading - a bit under 20 and a bit erratic. See
https://youtube.com/shorts/rNlBF5zRZ...CGHTGhmkAtI-st
Then, after maybe 20 minutes of idling, it was very hard to hear any tapping. The engine was now fully warm and idling around 750-800 rpm.
Note, to catch the oil splashing, I placed tin foil on top of exhaust manifolds beside the head and then placed some cloths on top of tin foil. I checked the rockers on all cylinders. The rockers on cyl 1 and 3 were maybe a tiny bit looser than other cylinders - but , all cylinders seem close to the same.