[Spits] spitfire head questions

[Aaron Johnson]

Ok knowledge question

 

Spitfire heads, there are a lot of numbers.

 

Can someone tell the difference between the heads other than valve size.

 

ex: are big valve and small valve head ports the same other than valve size?

 

I know some have air injection ports, but those seem to be irrelevant. 

 

Just wondering if the ports are different, or if they are all the same 

 

aaron