OHV = Over Head Valves. The valves are operated by push rods from a cam
mounted in the block between the banks.
SOHC = Single Over Head Cam. The valves are operated by a cam mounted
in the head. (there are really two cams; one in each head; but this is
referred to as a single overhead cam when you are talking about a vee
configuration engine; a dual overhead cam vee engine would have two
cams in each head).
If you mean which used Explorer should you buy there were problems with the
SOHC engines' timing chains and tensioners from about '97 to '01 (I think).
I bought a '97 with the OHV engine and I'm happy. If the eighth digit in
the VIN number is an "E" the engine is a SOHC. If it is an "X" it is a OHV.
If you do a google.com search using "explorer SOHC timing chain" you should
find lots of information about the problem.
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