This is a special application adapter. Similar to our big port to small port 4ag adapter, but specifically designed not as a port adapter, but rather a TVIS delete plate.

The ports are straight cut through in the same size as the ports on the large port head. Thickness is exactly the same as the TVIS plate.

If you are looking at this adapter, you likely already have something custom in mind, such as a turbocharged 4AGE Big Port head, or super high flow big port with large cams and ITB's or such.