When asking an engine question it is best to post the model number of the engine since there are often more than one fitting the general description.
Some B&S Service Manuals indicate early engines may not have had caps on valves but I have never seen one and if one valve has a cap then both did originally.
Walt Conner
I agree, I will have to go to my shop to get info. The exhaust has a cap & the intake doesn't. I will get info & get back to you. Thanks
The model number you posted is the Sears mower model number. The engine model number is likely stamped into the valve cover and the answer is yes but I would expect the valve has been sticking is why/how the cap came off UNLESS this is second hand and you don't know what the previous owner did. The cap is probably in the sump.
Walt Conner