emac

Need a little help again, I have a 81SC with 110M on the clock. No oil leaks (believe it or not) No smoke etc. The car run great. The question is this. When I start it after she sits for a day, the engine is very smooth sounding. As it get warmer it get louder, and I hear slight knocking sounds. Knocking really isnt the proper way to describe the noise, but its better than pinging. I have had the valves adjusted and its the same. Again be advised this car run great, lots of power. I have never owned a air cooled before and wonder if this could be a normal sound?
Thanks in advance

Ernie