Allow Optional Coolant Bleed Line to Correct a Known Problem
#29673 from Nick Fuhs · Rule change · TB 20-12 (2020-12 Fastrack)
In GCR section 9.1.1.B.14.f.3, change as follows:
"The cylinder head must not be ported, polished or machined. The original casting must not be modified in any way or polished,
with the following exception: A pipe thread fitting may be installed at the top of the cylinder head with a return line to the swirl
tower to allow any trapped air or overheated coolant to escape."