I have4.3 with erratic oil pressure and a ticking noise that gets louder withrpm

?Sludge build-up in oil pick-up screen , causing restriction?.....

Hydraulic lifters are used in S-10 engines. When tapping occurs with hydraulic lifters, it occurs because the the lifter is either bleeding out oil to fast, or it is not getting the oil in to keep it extended and to maintain its solid push on the valve. WATCH https://www.youtube.com/watch?v=lorANZ1Tptw&list=PLXK-5gP3Ei29cvLw5tpgWszVVxuwuNcAg Because the lifter is operated by camshaft movement , an empty lifter will have a sloppy movement, and you will get a metal to meat slap. This is typically the lifter hitting the valve stem but often the cam & lifter can have this loose slapping contact too when engine speed is too high. So the ticking will go with engine speed. Have you checked the oil? Both for its looks & the level. First look at the oil to see if it's color is wrong. ( a coffee shake look would mean you have water in it) If it's good , feel the oil in between your fingers to see if is very slippery like it should be. Or if it too thin & watery. If it is very thin & no thick slippery feeling, then smell it for a gas smell.. If the oil is very thin & has a gas smell plan an oil /filter change If the oil seems to be ok, you still may have a faulty or dirty oil filter. Inside problems may be a hydraulic lifter that may have collapsed or totally failed. or A camshaft bearing my have gone. This would cause the lifter nearest to it to starve for oil. The oil pump itself could be having problems. OR sludge & varnish build up over time has caused one or more lifter to be sticking What I would do is 1st, I would plan an oil change & filter. But with the current oil , I would add a container of Marvel Mystery oil, & run it at an idle for about 30 to 45 minutes. If any lifters have varnish build up in them, and causing the lifter to stick , this will help dissolve it. Then do n oil change Being 20 years old I would also use a heavier oil than normally recommended.

Have the 'actual oil pressure' tested with a mechanical gauge!!! The oil pressure switches on these engines are a common problem!! Pressure drop is normal as engine warms up... At the time of the testing... Have the mechanic LISTEN to the "ticking noise"... 'IF' the test gauge shows very low or no oil pressure... THEN try to find out why!!!.. Anything else is just a guess....