The B & S "cool bore" engines are just a bare casting, fairly high silicone alloy. Requires special rings, and the pistons are chrome plated . They can last a long time, but you need to take care of them. I have a Allis Chalmers rider with a 2 cylinder 16hp briggs in it. I inherited it from my dad, he bought it in 1984, and passed in 2003. It got well used. I does burn a little oil but not much. still has good compression. The old flathead briggs often developed loose valve guides with oil burning.