Our Stage 2 head upgrade begins with an inspection of the seats, guides and valves. After the seat integrity inspection is completed the valves and seats are professionally machined and blended to provide maximum flow in an un-ported head to achieve power and concentricity without the cost of ported heads. This process offers superior flow and sealing over the OE or a SE head. Heads are decked and fully assembled, ready for installation. Before decking approximate cc volume 89-90 cc