Thread: 3.5 v8 Dead - options

The 3.5 in the 101 may have had a different thread for the oil filter, I don't know when they changed to 3/4 UNF across the board (late 70s?). You should able to use either the oil pump cover off the 3.5 or the actual adaptor and swap them onto the 3.9. Make sure you have the correct gasket on hand before you swap the pump cover, they're a critical thickness.

The 3.9 when fitted in the Rangy has a spacer plate under the filter that the oil cooler pipe work connects to. If yours has the original 101 upside down filter housing fitted you could replace it with the rangy one and fit a remote filter as I have done plumbing in the cooler too. If it has the original 3.9 filter housing with filter pointing down they have probably taken the oil cooler adaptor out to give more diff clearance

Unless the 3.9 is a Serpentine front end (which I'm quite sure it isn't) the 101 filter head will fit straight on, bolt lengths are different so you'll need to use the original bolts for the 101 filter head, but it keeps things pretty standard.

If you've got the filter head off the engine then check the face that goes against the gears for wear, and smooth it flat with some wet and dry on a surface table. Wear on the face of the filter head will cause low oil pressure.