[DeTomaso] combustion camber design

[JDeRyke at aol.com]

Combustion chambers today in all high production engines are designed with 
the following three primary key elements in mind:

1. Complete as possible combustion within the engine to lower emissions, so 
to meet government requirements.
2. Fuel economy, so to meet government requirements.
3. Power, to reduce powertrain size and weight, so to meet government 
requirements.

-A- Hotrodders reverse #1 and 3 in the above list. 
-B- a rule-of-thumb measure of combustion chamber efficiency is how much 
ignition advance is  required for best power. Less advance needed= better 
efficiency, and vice-versa. Examples: F-1 engines use somewhere around 12 
degrees, '60s Chrysler Hemis used up to 50 degrees, stagger-valve Clevelands 
w/quench chambers use around 32-34 degrees, straight-valve LT-1 Chevs use as much 
as 40 degrees and LS-series EFI Chevs with Cleveland-type chambers & valves 
seem to need only 28-30 degrees. 
The above generalized numbers are all stabilized timing on various dynos 
with fully warmed engines. Radical cam changes in any of the above can 
seriously change the numbers, and they are not valid for drag racing where 
flash-timing with cool engines may be much different.   I'm really looking forward 
to Dan Jones' dyno runs! FWIW- J Deryke


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