Adjusting wide open lens aperture

I have a old K (pre-ai) 50mm 1.4 lens. The aperture at 1.4 is not wide open, when mounted on a camera and pressing stop down lever the aperture blades stick out a bit. All my other lenses don't have visible aperture blades wide open so I think this is not as intended...

I already relubricated the dry focusing helicoids, but I can't understand what to do with the aperture. Do I need to adjust the lens barrel or the outer casing (where helicoids are) somehow?

It's easy enough to find information on how to dismantle lenses, clean their apertures etc. but I haven't experienced something like this before