Id suggest you try a simple test and swap out a couple push rods and their matched rockers that work, with those that don't ,in other cylinders, in working locations and carefully re-adjust ALL the rockers in question and see if that fixes the issues. clean all the push rods internally with pipe cleaners and carb cleaning solvent, and carefully visually inspect the rockers oil feed holes.
if clogged the visual inspection and cleaning plus location swap should help you locate the issues source.
there's a good chance the push rods or the oil feed holes in the rockers are partially blocked, if so the , non-oil flow in the individual rocker issue should follow the defective parts, or clear up if its simply mal adjusted
start the re-adjustment by backing off the rocker as the engine idles until it clicks audibly, then slowly tightened until the clicking stops at least twice as this will tend to free a stuck lifter.
BTW add a quart of marvel mystery oil, as it does tend to free sticky lifters
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SBI part # 181-1048. Big Block Chevrolet V8 Long Slot Steel Rocker Arm Set Of 16. 1 - Stamped Steel Long Slot Rocker Arm. Each Rocker Arm Kit Contains Long Slot For Up To. 560 Lift Or More. Fits All Big Block 366 396 402 427 454 From 1965 TO 1990.
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correctly adjusting valves
this is an area that causes many newer guys problems ,a slight clicking noise at idle in any hydraulic or solid lifter valve train is usually the result of clearances in the valve train, obviously you should have, some clearance, to allow oil flow thru the lifters to provide lubrication on...
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