Having installed the Mummert valley covers on the Y engines, I don’t recall any clearance issues with the oil breather caps.  Without looking at a Mummert valley cover on an engine, I’m going to say that you possibly just need a smaller diameter oil cap.

Lorena, Texas (South of Waco)

Good afternoon, all. I have run into a fitment issue and I am hoping for some assistance. I have installed Mummert's aluminum valley cover and Spotlite Kustom Accessories valve covers, but the oil filler tube is basically the same height as the valve cover, so I'm having trouble installing a breather cap. Can the oil filler tube be replaced for a longer one? Is there possibly a smaller breather cap that can be purchased? I can provide pictures of what I've got going on if need be. Any advice or information would be greatly appreciated.

Thanks,
David