It would depend on the gear ratio and transmission.
stock tires 235/70r16:
auto(O/D) with 3.55 gears =2160 rpms
auto(O/D) with 3.73gears = 2270 rpms
manual with 3.73s = 2360 rpms
The 2003 Ford Explorer has 12 valves.
The 2004 Ford Explorer has 12 valves.
The 2009 Ford Explorer has 12 valves.
The 2002 Ford Explorer has 12 valves.
The 2011 Ford Explorer has 24 valves.
The 2005 Ford Explorer has 12 valves.
The 2007 Ford Explorer has 12 valves.
The 2006 Ford Explorer has 12 valves.
The 2013 Ford Explorer has 24 valves.
The 2010 Ford Explorer has 12 valves.
The 2008 Ford Explorer has 12 valves.
The 2012 Ford Explorer has 24 valves.