The Red Baron seemed to be stuck at 115 MPH during the 2015 and 2016 race seasons, regardless of fueling and boost changes. We knew that the exhaust valves and ports were quite small compared to the intake, and appeared to be the limiting factor to processing more air and fuel to make more power.
During the 2016-17 off-season, The Red Baron cylinder heads were modified to enlarge the valve seats in order to incorporate larger valves from a 500-cc Moto Morini engine. The exhaust ports were also back cut through the cylinder head. Back-cutting the cylinder head removes the “shelf” at the base of the new enlarged valve seat and enlarges the port diameter that would otherwise restrict the airflow back to original OEM conditions. The 90-degree shelf would have introduced a ‘trip’ in the airflow causing turbulence that can have an overall detrimental effect. Back-cutting the entire exhaust port ensures the limitations of the smaller exhaust valves are fully addressed.
The 500-cc Morini exhaust valves are the largest that could be fit without crowding the intake valve and side wall of the combustion chamber. Crowding the side wall would effectively block flow if too close. Also, with closer valves, there is a heightened concern of thermal cracking between the intake and exhaust ports. Cooling remains a critical concern.
The valve diameter increased by 2 mm, from 18.9 mm to 20.9 mm, increasing the airflow when the valve is lifted. The effective area of airflow through the exhaust port is more accurate when the valve stem and valve stem guide are considered, which block airflow at the center of the port. The larger exhaust valves increased the effective area of airflow by nearly 25% (calculation below).
The enlarged exhaust valves and valve seats were also accompanied by a more aggressive camshaft and ignition timing. Together, this unlocked more speed! The Red Baron achieved its first record at El Mirage Dry Lake – 123.310 MPH – and finished as a Top 10 Motorcycle in the Gear Grinder club!
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