Since the oil filter takes a tiny volume of oil from the main oil gallery, strains it a little, and dumps it back into the oil pan, it has no effect at all on oil pressure. A lot of stovebolt engines were sold without a filter, since it was an extra cost dealer-installed option. The most common cause of low oil pressure and/or slow pressure buildup is worn connecting rod bearings. Drop the oil pan and inspect the bearings before you do any more damage to the engine.
Jerry
Good morning, Jerry,
Understood on the oil filter, it was just a thought while thinking through the issue. As always, thank you for your input!
