Does anyone know if there is an anti drain valve in the filter housing? The engine rattles for a few seconds after starting I was wondering if that might account for the noise?

I have had a problem before with one but it came up low oil pressure. Did you replace both the o rings?

Have you had camshaft checked out?

I've replaced the filter a few times since the rattle started a few years ago the tappets were replaced a while ago didnt make any difference, I was reading about filters with anti drain valves built that gave me the idea there might be one

As far as I know the little o ring does the anti drain part. With it being an old engine maybe the oil pump is a bit weak on cold start up, is it better with warm engine?

The rattle is caused by the ancient tappets, nothing to worry about.

It doesn't seem to make much of a difference