cams 98 silverado

I'm changing out the rockers and pushrods because of the ticking coming from the front driver cylinder. it sounds like exhaust rocker ticking or chattering. I already got new rocker arms, pushrods and shiny valve covers. Now, when im in reverse and the park brake is on, i got out to listen because thats when my truck is in low rpm. lower than idle in forward gears. and i hear some slight knocking. very slight but evident. at first i was pissed. then i thought. well its coming from that same ticking cylinder. so if the exhuast valve isnt opening or closing exactly as it needs to could it cause that faint knock? its only in reverse. not the trans nor is it the exhaust piping rattling. i made sure sadly it isnt. theres no knocks in idle park or drive just reverse. so can that noise be caused by chattering valvetrain? now my other guess is spark plugs. since i put them in last year but as a noob never gapped them myself but simply believed the manufacturer did it for me as the box said so. so, im putting in new spark plugs, acdelco ones. and gapped at the proper gap. could crappy plugs make a sound in a cylinder from uneven burn? and once more, the slight knock isnt happening constantly, like its audible then not then a little more its off and on. its a 350 small block probably a 2 bolt main in a 98 silverado. has 92885 miles on it and i take care of that motor. although, i just now thought about me switching to synthetic blend because thats all that was at the store and its high mileage. ive run 2 of those one quart engine flushes, one in january and another in april then a full 5 quart full flush. drained the pan then put in the full flush and ran 10 minutes. theres no oil leaking(knock on wood) and the only thing ive done to the motor thus far is cold air intake, and cut off muffler for a cherrybomb muffler. change oil 2000 miles. tell me im just an idiot and drain this crap oil and it will fix my issue and so will new rockers and push rods. hope thats all it is but help me. im still learning these things. thanks

cams 98 silverado

as strange as it is, it no longer does it. i did the exact same thing on a cold start up, warming and running temp. nothing. went to class and came back and hunted for any faint differences. i know my engines noise and vibrations so anything different i notice fast. just a few minutes ago i popped the hood and looked under before i moved my truck. at first i thought my spark plugs were loose because i could see blue light coming from the plugs. then i realized that in pitch blackness, you can really see the firing of the spark plugs and when you touch the wires it lights up where you touch i thought that was soooo amazing. but along with all that i think i was wrong and my exhaust was just rattling because the only change in the testing was the initial one was in a one car garage where i cant open the doors fully so the sounds echo. the other tests were outside so im guessing i just heard the exhaust echo. but if i ever hear it again im taking your advice. now what do you mean by take a tee. like a tee hose fitting? where would i hook up an oil pressure gauge? thanks for your help