This is a very specialized area in tuning engines. Most street driven cars can benefit from a mild porting and polishing of the inlet and exhaust ports. The benefit being that at the factory the ports, when cast, can be extremely rough and restrictive to air / gas flow.
When worked on it makes the engine so much more efficient, (by allowing air / gas to pass through so much more easily - this term is known as Gas flowing), that it actually reduces fuel consumption and makes the engine respond and perform much better.
In cases where the customer demands considerably higher power levels, then the size and shape of the ports is increased and very often ports change shape. This is an art best left to experts who have gained knowledge by years of success. This job cannot be done at an amateur level. By changing size or shape slightly in the wrong place, you can destroy a perfectly good cylinder head.
One of our fully ported cylinder heads.
Valves and valve guides can also be modified in the same manner and very often the materials that they are made of, due to the demands imposed by the power levels, require superior metals to be used in their construction.
We always have cylinder heads in the workshop undergoing modifications, including valve guides that we make ourselves from our own blend of metals, this material is self lubricating, which means that tighter clearances can be used, this is beneficial for several reasons. Customers are very welcome to see the work in progress.
3 angle valve seats and swirl polishing of the valve heads are very common on engines with higher power levels, we have all the equipment and knowledge to perform a multitude of modifications to any engine.