After finding a cylinder head that met the basic criteria of a good piece of aluminum; it was time to decide just what to do to it to make it a better piece of aluminum: it was time for a plan.
A view of #1 cylinder combustion chamber of the head chosen.
The slight brinelling from the headgasket fire ring is evident; as is several spots of pitting around the ring. This head is within 0.002in of being totally flat. Resurfacing to restore total flatness should be under 0.010in. It came out as 0.007in.
This is going to be part of a tight squish engine. The tight squish will help cool the areas of aluminum within the fire ring. That protrusion to the left of the spark plug hole extends beyond the crown of the piston and out above the piston dish. That is a potential hot spot. I will smooth that back some to reduce the protrusion so that it is just to the edge of the dish.
Above the intake valve there is a very small step at the roof of the CC...another potential hot spot. That will be ground down flush. The surface around the valve seat inserts will be scraped to make sure there is no edges to become hot spots.
The tight squish of 0.037in will be within the boundary layer effect/proximity cooling effect distance of 0.040in. This also reduces endgas burning areas by turning those close proximity areas into quench areas. The head material will run cooler; and the piston crown covered by the sqush areas will also run cooler...potentially 200-300 degreesF cooler at the ringlands. This will keep the piston rings cooler. A win-win-win situation.
The tight squish will also assist in promoting a fast burn via enhanced turbulence and by reducing the size of the burn chamber. Fast burn also reduces piston crown temps. Now we have a win-win-win-win situation.
I am not going to "unshroud the valves". I would prefer to have the squish areas to completely cover the ringland areas; even if that squish area is only about 0.080in wide closest to the valves. Every bit helps to reduce the heat strain on the ringlands and the rings. The cooler I can keep my aluminum components, the more strength they retain, and the longer they will live.
