I was looking up tractor stuff on ebay found a book for a bgs what dose the 's' stand for?
During WW2 Hercules made a bunch of JXC engines speced specially for studebaker trucks. The war ended and Studebaker didn't need the engines anymore, or at least as many as ordered. Hercules made a deal with Cletrac to buy the excess JXC engines. Thats where the S came from. There is nothing different from the BG and BGS, other than the BGS will have a couple extra bosses on the engine for generator or other such parts that Cletracs didn't need anyway. They will probably have better balanced cranks for the higher rpms of the truck. Other than that everything is the same, other than minor modernizing of seals and such.
Bob
PS This came from a very reliable source that has delt with Hercules engines for many many years.