After warming up, my 1928 Gardner with the 225 cu. in. Lycoming 8 (GT series motor) is making some top end noise that sounds like a stuck lifter. It runs fine, and you only hear it when it idles, but you really notice it when you shut the motor down. When you turn off the ignition, you hear 3 bell like "tap,tap,taps". It sounds like it's from the front of the valve train. I just checked all valve clearances, and only cylinder #3 needed adjustment. Assuming I can isolate which valve is causing the noise, what's the easiest way to fix it?