Gary-
An OK source of info on exhaust tuning is in A. Graham Bell's (not the
telephone/Nat'l Geographic guy) book "Four-Stroke Performance Tuning." It
talks about designing your exhaust (primary, secondary, collector, and
tailpipe lengths and diameters) to optimize for various performance
characteristics (e.g. low-end torque, max power at high-end, etc.). It
provides tables and formulas to help with designing, and is available in book
stores, libraries, and by mail order. In the chapter on exhaust, it's a bit
short on theory, so check out other sources to get a good grip on acoustics
and gas flow. The book is a good reference, though, as it covers all aspects
of 4-stroke engine tuning.
-Paul Geithner
Arnold, Maryland
'78 Spitfire
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