The small bore on anything bigger than a 10 mil Cub would probably hold too much heat. The BB should get rid of heat better; however I've ran both on my 10 mil Cub and didn't make any difference at the track. It ran leaner at part throttle with the BB pipes, so that probably negated any effect on the heat. On the dyno the SBs peaked about 400-600 rpm higher, but the max hp was about the same. THese results will vary depending on exhaust duration, of course. Mine is only about 192*. Neither pipe utilizes the potential hp of my engine.