Originally posted by N1_STYLEz
...and the head has a 5 angle valve job instead of a 3 angle(this might be a stupid question but what do valve jobs do? do they add power or do they just reseal?)
Another important aspect of headwork is the valve job. Believe it or not, over 50% of the flow gains generated by good headwork can be found in the valve job. Factory valve jobs often involve only cutting the seat i.e., the 45-degree surface that the valves seal to. Sometimes there are additional rough cuts made to the port to ease the air’s approach angle to the valve. This is why factory valve jobs are usually either called one or two angle, one angle being just the seat surface, two angle being a seat surface plus a smoothing throat cut. In a cost conscious, mass production environment, there is simply no time or money to spend on small details like a multi angle, precision valve jobs...
If you want to read more on that you can find it here :
http://www.nissanperformancemag.com/december03/nerds/