I was cleaning out my dads shed this morning and found a used FL400S. I used his dremel to open it up. Here is my 1st cut and post oil filter.

Looks good sir:)

Thank You for the C&P

Looks like media is torn in one place. Did this happen in service or as a result of your cutting?

What are your thoughts on the filter after cutting it open?

Any idea on how many miles it was in service for?

I don't know. What am I looking for? I just was doing what every body did here.

What place? I put the filter in the trash but can go get it back. Where are you talking about?

I asked pops and he said he didnt even know it waqs in his shed.

6th photo - right side. Maybe it's just a light reflection playing tricks on me?

Look's like a hole to me...

Nice job. Looks like a classic tear to me.

The 'hole' has a reflection. That's oil pooling, probably atop glue. Though the same my first glance.

Good job on your first c&p

Yes not a tear, just a pool of oil at the seam.

The FL400s is the best of the Motorcraft filters.

+1 Agreed, a good C&P. Good on you for doing a cut & post.

I look for holes or tears in the media, damaged ADBV, damaged or in operative bypass valve. How well the media was glued. The integrity of the end caps. Excessive pleat distortion that might lead to a failure under slightly different operating conditions. Anything out of the ordinary. I look at what the filter trapped to decide on future maintenance. I view this as an opportunity to see what is happening in the engine without having to remove a valve cover or the oil pan. Was rust present in the can.

I probably left something out but this is a start. Enjoy the habit.

In the aviation business, we always cut open filters to look for metal bits. You could save a life.

Lycoming piston pin plug wear results in long slivers of aluminum in the pleats.
When you see that, you know you'll be pulling cylinders off soon.