Stock 350's have hydraulic lifters, so feeler gauges aren't needed. Get yourself a Chilton's manual or similar and read up on the valve adjustment process.
If a feeler gauge won't fit between the valve adjustment and the screw is fully backed out, it's possible that the valve clearance is incorrect or there may be an issue with the valve train components. Try rotating the engine to a different position and rechecking the valve clearance. If the issue persists, it may require further inspection or adjustment by a qualified mechanic.
To adjust the valve clearance on a 1998 Chevy Metro with a 4-cylinder engine, first, ensure the engine is cold and remove the valve cover. Rotate the crankshaft to align the timing mark to TDC (top dead center) on the compression stroke for the cylinder you’re adjusting. Use a feeler gauge to check the clearance between the rocker arm and the valve stem; it should be within the specified range (usually around 0.008 inches for intake and 0.010 inches for exhaust). If adjustments are needed, loosen the lock nut and turn the adjustment screw to achieve the correct clearance, then recheck with the feeler gauge and reassemble the valve cover.
the clearance is measured at the top of the bearing with the help of a feeler gauge
By the use of feeler gauge and with dial indicator as possible.
I believe the clearance should be within .002 and .007 thousands of an inch. and also the end play clearance, should be between .002 and .007. you should check the bearing caps with plastic gauge, and the end play wiyh a feeler gauge.
Valve clearance of Volvo f12, are set using a feeler gauge on the lash adjuster.
The valves are adjusted by loosening a 10 mm jam nut and checking the clearance with a feeler gauge. A certain procedure must be followed. Just Google "denlors valve adjustment article" for detailed "how to" instructions for most 4cyl Honda engines.
17mm of the feeler gauge for intake and exhaust valves
To check the valve adjustment clearance on a Mazda B3000 V6 engine, first ensure the engine is cool and disconnect the battery. Remove the valve cover to access the rocker arms and pushrods. Use a feeler gauge to measure the clearance between the rocker arm and the valve stem, adjusting as necessary to achieve the specified clearance. Consult the service manual for the correct clearance specifications and adjustment procedure.
feeler gauge
The Valve clearance for a 1993 TRX Honda Fourtrax is 0.03 on a feeler gauge. 0.03 -intake 0.03-exhaust
If you're going stock lifters, they're hydraulic and you don't mess with them. If you've replaced with solids (which is a really good idea), you'll need to get that information from the people who manufactured the lifters/cam.