What are acceptable Knock readings?

Under high load (WOT) it's normal for the Knock readings to stay in the 400's and reach into the low 500's. As long as your readings are staying below 550, your engine should be fine. The key is to look for large spikes in the readings in your datalogs. If it suddenly jumps from 400 to 600+ then you may need to pull some Ignition Advance in that Cam Angle table around that RPM. Always run the highest unleaded octane fuel available in your area to help keep premature detonation from occuring.