Originally Posted by brenx
Even though these have 4V port locations I think you'll find deficiences in the cast iron 4V's have been reduced in the alloy version. For example : The opening might be the same size but the runner won't be.
From what I can see, this is what is happening. The port gets smaller the further you move into the head. It's a bit hard to tell with the top one on the angle though.
Actually If you look at a cross section of an iron 4V head it dramatically tapers upwards from the manifold face to the tight radius in a similar fashion, the port fillers actually fill this area to leave the top 3/4 of the port to flow.
As you know the iron 4v port is higher in the head than the 2V port hence it gives a straighter shot at the valve.
Ill be very interested to see how this head performs against the 2V and 3V versions.
Am i correct to assume the 3V version is just a copy of filled iron 4V port placement? (obviously with better shapes and better exhaust port.