Originally Posted by Silver Surfer
I have read that adding larger valves to Vortecs is bad because it decreases intake charge velocity. Also the casting is pretty thin and close to the water jacket and cutting for larger valves increases chances of a crack developing — which is also a factor that needs consideration when porting Vortecs. The intake flow numbers for Vortecs are pretty awesome. They are lackluster in exhaust flow, so if you port, do the exhaust side.
Their exhaust flow really isn't "lack luster" when compared to any other OEM castings, and the fact that they don't have a exhaust crossover is a huge plus. They're way down compared to an aftermarket head, but no bad for a stock as cast OEM head.