I also have an early Super Cub that came from the factory as a 105 in 1950 but not a 105 Special. I took an early narrow deck 0-320-no suffix, 150 hp engine and built it into a -B2B 160 hp. There are two issues potentially:
1. Approval for installing a 160 hp 0-320 engine on a Super Cub airframe.
Since the Super Cub Aircraft Specification No. 1A2 does not list a 160hp engine in the specification, installing a 160hp engine is a Major alteration to the airframe. A 337 is required to install the B2B or just about any other 160 hp engine in the Super Cub. STC SA00522SE (installation of a 160hp engine in a Super Cub) is available for purchas from Cub Crafters and the change must be reported for approval on a 337.
2. Rebuilding a 150 hp 0-320 into a 160 hp engine. This does not require an STC or a 337 ( as long as all internal & external parts exactly match the new suffix bill of material), just the stamping of the engine data plate with a "C" as spelled out in a Lycoming Service Instruction SI-1304J available on line, just Google it. Then with a log book entry explain why the "C" was added to the data plate. Below, I reference going from an A2A to a B2B but any 150 to 160 hp change would follow the same logic.
Since most people would believe that a 337 is required, here is the logic string that proves the point.
A. FAR 1.1, General Definitions, states: Major Alternation means an alternation not listed in the aircraft, aircraft engine, or propeller specification. The key point – if the alteration is listed in the engine specification then it is not considered to be a major alteration.
B. FAR 43, Appendix A - Major Alterations, Major Repairs, and Preventive Maintenance, states: (2) Powerplant Major Alterations. The following alterations of a powerplant when not listed in the engine specifications issued by the FAA are powerplant major alterations. The FAR goes on to list examples of major alteration including a compression change but the point once again is that the list of major alterations is applicable only if the change is not included in the engine specification.
C. Type Certificate Data Sheet No. E-274 is the FAA certification document for the 0-320 engine. All engine models listed in the document lie within 0-320 engine specifications. In the TC block on each engine data plate “274” appears for all 0-320 engines listed in the E-274 document. Revision 15 to E-274 dated February 19, 1998, lists 59 engine models that fall within this engine specification including 0-320-A2A and 0-320-B2B. Therefore converting an –A2A to a –B2B is a change within the engine specification and qualifies as a minor change.
I hope this helps, Darrel