The lower duct is a ram air system. The ram air intake plenum is Kevlar, and is a true divergent cone that has an approximate 33sq in cross section at the front and gradually increases to a 36sq in cross section where it feeds twin 5" tubes to a ram air box on top of the motor. The ram air box contains a 14x5 round air filter and sits on top of a 1200cfm throttle body injection. The entire system is designed such that the cross section (inside volume) gradually increases up to the throttle body. This increase in cross section causes the air to gradually slow and pressure to rise as it approaches the throttle body.
Oil temperature control is handled with an
oil/water heat exchanger.
RE radiator angle: Heat exchanger core placement within a duct is a complex issue with no easy answer, conversely, one mounting direction is not inherently superior to another as everything is contained within the duct. This design was driven by the stock 427 radiator opening of about 220sq in.
Heat exchanger core size is determined by calculating the percentage of core that is blocked, and upsizing to have at least 220sq of open space. It just so happens that Gordon Levy's racing radiator was just about right. Having the core angled allows for a smaller divergent duct on the intake side. The heat exchanger packaging restrictions determined mounting angle direction. Mounting the heat exchanger perpendicular to airflow necessitates either too radical a divergent duct for the large core, or too small a core for proper flow. It is very rare that a proper heat exchanger would be mounted perpendicular to airflow. Simply making the core thicker may give more surface area, but it will also restrict flow through the duct.
In this design, I had some packaging restrictions. The short nose and X brace on the frame limited options for heat exchanger exit duct location and angle. This dictated that the lower section of the heat exchanger core be forward. This design has a divergent duct from the intake to the heat exchanger core, and then a convergent duct to the hood exit. The hood exit has the same cross section as the intake.
Here is a design concept sketch. You can see more details at ffcars, but I don't really want to do a build thread on this site until later.
