I have removed the belts. the noise seems to be coming from near cylinder 8 using the screwdriver method. I have pulled the number 8 spark plug and inserted a metal rod with a magnetic end on it trying to see if something had somehow gotten into that cylinder. I rotated the engine a little bit at a time while using the magnetic pickup but didn't find anything there. The valve covers are listed as being "Tall" covers but I will pull the valve cover from that side tomorrow hopefully if it doesn't rain.Have you removed all the belts to eliminate noise coming from any pulleys, or the fan. Also unbolt torque converter from the flex plate and push it back towards trans for clearance; assuming it's an auto.
Are the valve covers the same as when it was run out of car? Maybe roller style rockers are hitting inside of covers, and they need to be taller.
Get a long screwdriver or actual engine stethoscope see if you can determine if the noise is top of engine, left or right valve cover, front timing cover or from bottom or in oil pan area.
Use a cylinder balance analyzer (kinda old school, analog tach/dwell meter style, Craftsman had one back in the day) and see if killing one cylinder at a time changes or isolates the noise to a particular cylinder(s).
If you don't have one, you can use test light and some short pieces of vacuum line between spark plug wires and cap to kill spark. Some guys like to poke holes in the boots on the distributor cap but I don't like doing that.
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