The gory details revealed…

1 Cutting out old exhaust valve seats

Starting with the bare head casting, the first step is to cut out the old exhaust valve seats, creating pockets for the hardened steel inserts.

2 Fitting hardened inserts

The inserts are immersed in liquid nitrogen at -196oc and, while still cold, they’re hammered into the pockets in the head.

4 Cutting exhaust seats

A different cutting head forms a 45o seat in the inserts, which fit flush with the roofs of the combustion chambers.

3 Cutting new inlet seats

Back on the Serdi machine, Giulio recuts the inlet valve seats. A triple angle cutter gives the optimum profile for gas flow.

5 Quality control

The heights of each valve are measured. Another test is to pull a vacuum behind each valve, ensuring there’s no leakage.

6 Refacing the heads

Both the cylinder heads were slightly warped, needing four thou to be skimmed off using two passes from the milling machine’s cutting head. After that, they were finished by fitting new core plugs, assembling the valves and springs, and finally painting.