You could be hearing piston knock. At light loads, looseness between the piston and the bore makes a higher pitched knock than a rod. Usually gets better under load. It is also louder when cold and quieter when hot.
A loose piston pin will also knock but won’t be as affected by temperature. If tbe looseness is between the pin and piston it will get worse when hot. If is between the pin and connecting rod, it will knock all the time. Both tend to quiet under load and knock at idle.