Not absolutely sure but I think the notch goes on the cam side. There are three heads for the 270. The old style dome chamber with small ports, the old style dome chamber with big ports called the H head, and the later sort of D shaped chamber but not like the 302 D chamber. The late 270 head has small ports. Of course different chambers could use different pistons. Sadly 270 pistons are becoming hard to find. The small ports are adequate for for ant street engine.
