Curious; Difference between Large/Small Port CIS Airbox

[Tidybuoy]

I'm just educating myself. I've seen several CIS airboxes for sale on the classified and some say large port.

I'm assuming the large port is for the 3.0 but do any people install these on the 2.7 for improved breathing.

Just wondering....

[snbush67]

The outlets on the airbox should match the diameter of your intake runners and intake ports.

Using different sizes will not increase the performance.

[Laneco]

Originally Posted by Tidybuoy

I'm just educating myself. I've seen several CIS airboxes for sale on the classified and some say large port.

I'm assuming the large port is for the 3.0 but do any people install these on the 2.7 for improved breathing.

Just wondering....

3.0 engines are large port or small port. 78 and 79 are large port. 80 through 83 are small port. HP in the US was the same but the small port engines are slightly higher compression at least in the US. The large port air box and runners are desirable to people who are choosing to do upgrades for more power (including porting the small port heads) but want to retain CIS.

angela