Manifold Headers for MG MGB (1962-1980) 1.8L EngineHigh Flow Manifold Headers for 1962 1980 MG MGB (B Series ADO23) What It Does: Replaces the restrictive factory cast iron manifold and downpipe with a high velocity 4 1 stainless steel system to improve exhaust scavenging and increase engine efficiency. The Stock MGB Weakness The factory exhaust manifold on the BMC B Series engine is a significant performance bottleneck. Constructed from heavy cast iron, the OEM unit features a restrictive "log"