The most important thing any engine builder needs to know is which machine shop to use.  There may be only a couple of machine shops in your area that do the kind of work you need to be done but that doesn't mean they are qualified.  Joe's Machine Shop has been owner operated for 30+ years.  He is a modest and patient guy.  His shop is on Austin Drive in Decatur, GA and you can reach him at: (404) 288-7612.  The block had been sitting in an unused corner of a garage for several years.    Joe bored it .040 over and installed new cam bushings.

Not every application calls for a five angle valve job or a radius valve job.  Although it produces better flow around the valve seat and better breathing.  It's not always how big the engine is but how well it breaths that makes the difference in performance.  In this shot we see Joe has put a rounded or radius valve job on the heads.  When blowing into an engine with twin turbochargers, the number of angles on the valve job doesn't make a whole lot of difference.  If we were racing a group of Hummers with similar race preparation it would be mandatory but this is, after all, a rather unique application.

Notice that we are using the low compression heads.  These are looked over by the guys building normally aspirated engines since they want high compression ratios.  A turbocharged engine can run higher boost without problems only with low compression.  The next step is porting.   We spent around 90 hours on these heads although when you are blowing through an engine, porting and polishing is not that much of an improvement for your time spent. 

So after smoothing out the edges and enlarging the area around the valves we'll stop.  It isn't necessary to polish for street applications anyway.  In fact, some race teams don't polish even for all-out events because they believe it gives better atomization of the fuel to pass over the semi-rough surfaces.  The most important thing is to remove rough edges that can glow red hot and cause detonation.