is if the motor slows down or loses RPM when you pull the pipe up (shorten it). If this should be the response when pulling the pipe up get it back quickly as you can burn or stick a piston quickly with too short a pipe.

Reading plugs will give you a lot of information, and the Jennings book you have, although somewhat out of date, is a gold mine of information.

There are also web sites that have information on correct lengths, angles, stinger and header pipe size for various applications, but the most specific of those formulas require disassembly of the engine and careful measurement of various internal dimensions of the engine, plus a target RPM range you want the motor to run in.

Gordon Blair is one person who has computer programs on expansion chamber design.

Good Ludk