Yep, crankcase breather. I can tell you what I've seen a few times, I just finished a 1275 that I built for a guy who bought a bugwye for restoration that already had this 1275 in it, problem was that for some odd reason had retianed the 948 timing cover and now the engine had no crankcase breathing, needless to say I swithced to breather type 175 timing cover.