Somewhere on the engine, usually stamped into one of the rocker covers is the model type & code numbers.
Go to the B &S web page, support section and using the model & type numbers download your engine parts book.
Check the head page for lash caps on the ends of the valves.
Never seen a B & S engine without them then again I have never seen a lot of things.
Post those numbers and you will get a lot better help.