Because they are Ford cars, modified by Shelby.
Shelby drives a very crappy ford because ford sucks
The 2007 Ford Shelby-GT500 has a V8 engine.
The 2014 Ford Shelby-GT500 has a V8 engine.
The 2012 Ford Shelby-GT500 has a V8 engine.
The 2011 Ford Shelby-GT500 has a V8 engine.
The 2011 Ford Shelby-GT500 has 32 valves.
The 2014 Ford Shelby-GT500 has 32 valves.
The 2010 Ford Shelby-GT500 has a V8 engine.
The 2012 Ford Shelby-GT500 has 32 valves.
The 2013 Ford Shelby-GT500 has 32 valves.
The 2008 Ford Shelby-GT500 has 32 valves.