Valve tapping ccan I fix it myself before I take it to mechanic

Inspect/Test/Service/Replace Hydraulic lifters can fail for several reasons:

• Dirt lodged in the check valve can allow the lifter to leak. Too much wear between the lifter and the body can cause excessive leak-down. This results in a noisy lifter.
• A lifter might be noisy because of an oil pressure problem.

NOTE An oil pressure problem will be evident on hollow pushrod engines if no oil is reaching the rocker arms.

• A lifter can become stuck because of varnish that accumulates between its plunger and body due to a lack of periodic oil changes.
• A stuck lifter can sometimes be freed up by the addition of an additive to the oil, or by spraying fuel system spray cleaner down a hollow pushrod oil channel.
• Lifters that stick because of varnish buildup can sometimes be loosened up by squirting carburetor spray cleaner down the hollow pushrod lubricating channel, where it contacts the rocker arm.

Hydraulic lifters are not rebuilt because they are relatively inexpensive. It is possible to disassemble and clean lifters but they must be reassembled with their mated parts. Because of the labor time involved, this procedure is usually impractical.
Sometimes a piece of foreign material becomes lodged in the lifter check valve. If the lifter is removed and disassembled before serious wear between the lifter and cam lobe results, it may be cleaned.
Worn mechanical (solid) lifters can be reground.

• The base of the lifter is ground to a radius on a special lifter grinder.
• Roller lifters have a longer service life than standard lifters.
• Wear can occur on the roller pin. Some of these pins are serviceable.

It might occasionally be necessary to disassemble a hydraulic lifter to clean it or to inspect it.

• If this is necessary, disassemble one lifter at a time and pay attention to the order of the check valve assembly.
• Lifter disassembly is done by pressing down on the pushrod seat with your thumb and using a screwdriver to remove the snap ring.
• Remove the plunger from the body; this may require tapping the body.
• Next, remove the check valve assembly.
• After thoroughly cleaning the lifter components in solvent, visually inspect them for signs of wear.
• If the internal components pass inspection, the lifter can be reassembled.
• During reassembly, cleanliness of the parts is of utmost importance.