Its a funny thing Im learning in Japan, the stuff online seems
to be for the consumer but the racers use their own version of
combustions chambers to get more from these ports.
If everything is available to the privateer then big wigs lose
Nissan did the same with the FIA heads intentionally made things
hard for the privateer to beat the guys making them.
I believe there is secret squirrel stuff in the A series Pitroad practice
in not showing they use popular aftermarket pushrod v8 style chambers like
the ones below
http://www.lsxtv.com/news/frankenstei ... r-all-out-ls-performance/supposedly the A series chamber produces too much swirl for extracting peak hp and since v8 2v chamber development has way more up its sleeve, I wont be surprised this is what they are using.
Jmac prob could chime in here and I also noted an L series engine built by a skilled head porter he recommended to me used the david vizard style 2v chamber used on most aftermarket chevy and ford heads with good results for an otherwise L series novice - albeit with the help from L series gurus combined with his V8 background.
The hours that goes behind these heads to get them to make 130hp per litre is well beyond the skill, time and budget of most peeps.