All of the machine work is done right here at our facility by Giuseppe and Giuseppe.
One of the steps in rebuilding any cylinder head is to seat the valves. After the new guides are installed and the seats are resurfaced according to the position of the new valve guides, the valves are seated to ensure a perfect fit with the seat. This step ensures ideal compression in the chamber. Proper valve seating keeps air from leaking out of the chamber and into either the exhaust and/or the intake system.
The final step before reinstalling the valves, seals and camshafts, is to resurface the cylinder head surface. Often cars that overheat have a warped head surface. And cars that have been driven extensively with a faulty head gasket tend to have a pitted head surface. As with the seat reseating process, the cylinder head also needs to have a "true" and "level" surface to insure compression at the head gasket.
This cylinder head was slightly warped as well as having some minor pitting.
The uneven surface is evident once the milling machine has made a few passes. The machine shaves the surface by approximately .001" with each pass. You can see that this particular head was warped at the center/intake side. The shiny area is where the millinf blade has shaved the surface and the darkened area is where the old head gasket once sat and some pitting had taken place.
The final pass of the milling machine produces and even, smooth, polished surface. From this point on, we can go ahead and reinstall all of the head components.