Total advance question

Mattax said

Detonation under load - you'll hear the engine pinging. If you hear it at wide open throttle, back off immediately.
If you hear it at light part throttle acceleration, not so bad, although you still would want to correct the situation.
Too much timing at steady cruising speedy and the engine may buck a little - some people call it trailer hitching or fish biting.

If you are concerned about detonation, you can check the spark plug porcelain for shiny specks of aluminum.

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Only noise I have heard started in the past few days and only at idle after the engine starts to warm up not when cold. A strange high frequency noise that very short in duration but regular and goes away when you increase rpms above idle. Noise comes out the breather cap. If you cover up the breather cap with your hands you don't hear it. Can't hear it with a screw driver on valve cover, block on that side, exhaust on that side or intake. Haven't heard a ping in years would think it wouldn't be this high.

Doing some research on noise sounds like a lifter. Starts when oil starts to warm up and going away when increase rpm which increases oil flow. Too high pitched for rockers.