The next step begins by renewing the exhaust seats with hardened inserts. Recesses are machined into the head and new hardened inserts are pressed in place. If proven unserviceable by other means, the same process will be used for inlet seats as well (Photo shows head with both inlet and exhaust seats replaced).

   After the new seats are installed, we remove the old guides to allow proper access to all areas of the ports for modification. As can be seen, port modifications are extensive and these before and after views of the exhaust ports are especially revealing.

   With the majority of port modifications complete, the new bronze guides are installed and clearanced for final size and finish. The guides are first reamed and then final-honed to within half-thousandths inch increments to complement valve stem size.

   After final guide preparation is complete, the head is ready to have the valve seats cut. We use specialized tooling and machinery to do a precise and infinitely repeatable job, after which the seats are hand blended to the ports. With this work either making or breaking the final performance of the cylinder head, the correct knowledge and experience are paramount.

   With all modifications complete, the head is cleaned and carefully assembled, before being taped up and redied for shipping.