Someone previously mentioned the basic tenet of determining OHV v.
OHC - the head either has a spark plug and fins (OHV) or a round
cover (OHC) on the left.

The older pushrod OHV (over head valve) engine uses long thin round
rods (pushrods) that reach from the cam in the crankcase to the head
to actuate the valves.

The OHC (over head cam) engine drives the valves with a chain or gear
driven cam in the head.

The round cover on the left side of the head is for access to the
driven cam gear - OHC.

The pushrod engine has fins on the left side - OHV.

Also - the pushrod OHV engine has an oddly-shaped rounded cover on
top of the head, the sparkplug on the LEFT side, and the cylinder has
fins on BOTH sides.

1960's C50 Pushrod OHV:
http://images.cmsnl.com/img/partslists/cylindercylinder-head-ca100-honda-50-us_b\
ighu0062e1401_de0a.gif

The OHV has a smooth side on the left side of the cylinder (cam chain
idler gear bolts in there), the round left side head cover (cam chain
driven gear) and a square, lightly finned cover on top of the head
(over the rocker arms).

1980 C70 OHC:
http://images.cmsnl.com/img/partslists/cylindercylinder-head-c70-passport-1980-u\
s_bighu0084e4a02_dccd.gif

Most low-tech American car engines are OHV. The cam is in the
crankcase, uses "lifters" that ride on the cam to translate the
rotating lobes into direct motion and long metal rods in the the top
of the lifters to reach the rocker arms in the head to actuate the
valves.

Higher-tech engines usually are OHC. Pushrods and lifters add extra
weight, add reciprocating mass (vibration), and a little greater
chance of failure (bent rods). OHC engines turn easier and have less
vibration, so they usually rev considerably higher.

Confusing point, but easily straightened out - almost all engines are
OHV (except older lamn mowers, flathead Harleys and things with no
valves like rotary's and 2-strokes), as the valves are over the head
- OHC included (valves are indeed over the head).

In an OHC, the one thing that's different is that the cam is on top
of the engine, and the rocker arms ride directly on it to actuate the
valves (no pushrods). BM