This is the best book that I have found so far. It is a practical, hands on description of the Weber DCOE and Dellorto DHLA carburetors. It covers a complete teardown and rebuild, setup and tuning, and problem solving. It is pretty good about keeping the Weber and Dellorto specific information separate. The only thing lacking is some of the theory of operation. You can purchase this book at Amazon.com

Author: Des Hammill

This book covers the Dellorto DRLA, FRD, and DHLA carburetors. Although it is light on information for the DHLA. Since it is written by CB Performance, it is very specific to VW applications which limits its usefulness for rotary tuning. The one area that this book has over the Hammill book, is that it includes a lot of information and diagrams showing the theory of operation. It more clearly describes which parts of the carburetor are in effect at various throttle positions and engine RPMs. You can purchase this book from CB Performance

Author: Bob Tomlinson