Does the size of the area where the air is pulled into the runners, plenum?, have a direct effect on power? Do you want it as small as possible, and would groves in the base allow for better air distribution at higher rpms?

Thanks
Jeremy

 

You want a fairly decent volume. I think the rule of thumb was about 1/2 of the displacement (I forget, and I'm sure someone will correct me). It acts as a reservoir for the air in between "Events" - i.e. Intake Valve 1 opens, draws air from the plenum, then 90 degrees later, Intake Valve 8 opens. If the plenum is too small, the airflow through the throttlebody will be pulsing with each event, rather than a steady (more efficient) flow into the plenum, where each runner can take air. There's been quite a bit of home-brew engineering with the LT1 and GrandNational guys playing with larger plenum volumes...