V6 Balance Shaft-Equipped Engines. Mild Street Performance with Slight Idle For Stock Converters with Aftermarket Intake and Headers. Adjustable Valve Train Required - For Carbureted Applications Balance shaft equipped 4.3L engines were introduced in '92 but GM continued to produce the previous version until '94. Non-balance shaft 4.3L's (' 85-'94) shared their timing cover with the small block Chevy V8 engine. The balance shaft 4.3L's timing cover is noticeably taller than the non-balance shaft version.