That must have been a newer (18hp) twin that was sick... Still have 2 I/C Briggs twins (Industrial - Commercial) 1-16 hp and 1-18 hp both still run great the newer one is an 18 hp 1983.
The 16 hp was built in the 70s
also picked up a good running 11.5 i/c single at an auction for a friend and it has an identical mower deck and drive system as the 18 hp and there is no way the 11.5 cuts as fast or with as much power as the 16hp or 18hp twins...
These are as stated- all pre 1985 mowers and the fact that neither of the twins have had any work other than a couple sets of plugs, oil changes and air filter changes and one carb kit@ $11 can't say what work the 11.5 hp has had but it also runs well, just not as strong as the twins , or as smooth... IMO Still think both designs are solid...do have one mower design that has been Nothing but expensive trouble - a 4518 Honda hydrastatic, liquid cooled vertical twin, riding mower
others may have had different results
