XK-120 Oil Pressure

The pressure relief spring adjuster is on the top right side of the oil filter housing. You remove the large brass dome nut, collect the washer under it, loosen the thin locknut and turn the large screw down while running the engine at 2000 rpm. You should set it at 40 psi with the engine fully warmed up.

Hi John,
The oil pressure in an engine is established by the oil pump flow, pressure relief spring setting (tention) and the amount of wear (or clearance) of the bearings or oil pump gears.
Before you go ANY FURTHER.....DON'T trust the oil pressure gauge reading! put another mechanical gauge on the main oil galley to confirm the numbers.
If confirmed then you have a couple of options to 'fix' the problem short of a rebuild.
The pressure relief spring for the oil pump can be adjusted, replaced or shimmed to increase the pressure at which it starts to relieve flow or pressure to the by-pass, this is in the assembley behind the oil filter where it bolts to the block.
Also try running a good quality motor oil with a weight of 20-50.
I would say a correct oil pressure for the 3.5 engine at idle (cold) is 20 PSI and (hot) at 15 PSI...at 2500 RPM 45 (cold) and 35-40 (hot).
One more thought, (and not trying to be too commercial). On any older engine I like to run an oil additive called "Mr.Moly- Engine Aide"...this is called 'MolySlip' in England and it can save an engine with low oil pressure by maintaining a 'moly' seperation between the bearing and crank/rods/cam etc.

Regards
Mike Leicester
Lesco Engine Machine

Thank You John

Art

That's about normal, although it should be 40 pounds at 2500 rpm. You can get it up a little by using 20-50 oil.