The process is called porting but what us DIYers are really doing is removing casting lumps, chunks, burrs and flash. It is good to contour the valve guides (Not remove them as some back in the day advised.) No "hogging out" just making the port and bowl what the factory would have liked to have done but were refrained by cost. Many will say to just buy some new aluminum heads. If one has good used heads with healthy guides and seats than porting yourself is the best way for great power and on a true working mans budget. Plus its true hot rodding.