Just look at the intake manifolds. The single port is a one piece manifold
with single "tubes" on both sides. The dual port is a 3 piece manifold (when
using the stock carb) and has double "tubes" going to the heads.

This is an example of a single port, notice there is just one tube going to
the head (the heat riser doesn't count).
http://www.i405.com/vw/stand/engine_alternator1.jpg

This is a dual port using the stock carb. Notice the red things with clamps
that keep the 3 piece manifold together. Also, there are twin tubes going to
the heads.
http://www.autoshoppingcenter.com/ge...uiltengine.jpg

This one is a dual port with double 2bbl carbs. This time there is no 3
piece manifold, but the intakes have twin ports.
http://www.thesamba.com/vw/classifieds/pix/574016.jpg

Hope it helps,
Karls

"Frank" t> wrote in
message ...
> I'm hunting for a Beetle and unfortunately it sometimes happens that the
> person placing the ad omits the "dp" from the ad.
>
> Is there an easy way, by looking at the photo of the engine, to deterime
> if
> it's a dual or, single port?
>
>
> Thanks,
> Frank
>
>
>