90* oil filter adapter????
How much torque are you putting on the bolt? I fortunately had my exhaust off when replacing mine and was able to get a torque wrench on it for the (40lb?) spec. This is one of those moments where exact tq is needed imo.
I’ve also seen a double gasket in the block recess where the adapter mates up. This was on my 273 that didn’t leak, but I had to use a thin flat blade to remove the hardened gasket material. It looked like the block until I started cleaning and scraping.
Just some extra ideas.