I recently bought a Snapper 924 which has a 9hp B&S model # 20C414. I asked the B&S email account if the 20C414 is an aluminum alloy (as the 20A412 is or cast iron as the 20D414 is). I received an email from B&S saying the 9 hp engine I mentioned is in fact cast iron for sleeve and that it is special order for Snapper. Engines in Snapper manual all have same displacement. B&S lists all as having same max rpm. so it has me wondering how do they get the extra horsepower. Mine does say 9 hp on label on engine, so I assume it is. Torque varies slightly from one to another- 13- 14 lbs of torque at about 2500 rpm. I asked if I should replace the regular oil with synthetic oil before the 2 hr break in-B&S email reply did not seem to be pushing synthetic- said I would do it after 8 hr break in. I told them I would use Mobil # 1 if they thought it was OK. They said that is fine.
That series of B&S OHV 9-12 hp is their premium engine- main difference seemed to be the premium parts and looks like cast iron sleeves.
You can get Champion platinum replacement plugs for the RC12YC which is the spark plug for the B&S at least the 9 hp.
It is not easy to get all the info in a straight forward manner from the web sites.
hidato