difference between the 4-port and the 6-port 12a
 

i wanted to know how to tell the difference between the 4-port and the 6-port 12a

The 6 port isn't a 12A it's a 13b. The 5th and 6th ports are designed to allow a later closing of the intake allowing more timing and hp.

If you have an engine disassembled (particularly the front and rear side plates), you will see a port on top of another port.

actually there is a 12a 6-port known as the 12a 6PI.
i'm looking for this engine .
can anyone tell me how do i spot this engine fully assembled ?
thanks.

You are correct that there was a six port 12A rather rare though. A friend of mine had one and the intake is very different than a four port. Look at the lower part of the manifold where it bolts up to the engine. You will see a difference at the secondary ports it will look much different. Hope this helps you out.

is it much wider compared to the 4 port?
and what car does it come in ?

The US market did not get the 6-port 12a, most of us are not familiar with them. Iirc the 6-port 12a has a butterfly style valve for the 2 aux ports. There should be some sort of extra hardware/ linkage associated with these ports. The front and rear intake manifold ports should be taller than the 4-ports. Hope this helps some.

thanks guys for all the help
there are no 13B 6-Port here in my country
hope to find a 12A 6-port for an all motor car