Hi guy! I posted about this in a different way but this is more basic.im 50 and seen lots of stuff but this doesnt make sense.my boy buys a s10 4.3 drives a week runs good,no smoke,engine smooth and absolutely no noise.checks oil decides to change.immediately starts knocking! Calls me i listen to it,knock comes and goes.pull plug wires no difference.well instead of diagnosing further like i should and normally would.i read up on 4.3.come up with balance shaft.long story short.install gm retro timing chain tensioner kit,new hv oil pump although oil psi was very good b4.lots of labor for nothing and 500 in parts!still same knock.i just dont see a doctored up engine running that quiet prior to oil change? Could a wrong bbrand/type filter? I thought of pulling tc cover and eliminating balance shaft gear? All that will do is a sligjt rough run.but the other thing is if it were a piston noise.i just wouldnt think an additive like stp,rislone etc would cover up for a week long enough to sell?i have a good 4.3 lined up but thought id ask on here before i go that route.thanks for any ideas in advance