Installed a mechanical oil pressure gauge, just used the unused vader light hole under the dash to mount the homemade bracket, so no new holes in dash. This to allow easy, no impact removal if needed. Still have the fully functional (and annoying) OEM idiot light.
At cold startup, was getting 42psi at idle, dropping to 5psi or less at idle after fully warmed, then barely to 20psi at 2k rpms. Oil pressure regulator was fully adjusted, so I shimmed the spring and now it’s 50psi cold and 25psi warmed and 2k rpms. Still drops to very low pressure at idle when fully warmed. (8 qts of 10w-30 Rotella T-4)
I have a smidgeon more adjustment I can make since shimming, then will test again. If no improvement I’m going to pull the regulator unit off to verify the plug is fully seating and to replace the o-ring gasket (Redline’s kit), but I doubt there’s issues therein, just want to check that box off. This is a really old motor, previous threads show what I’ve done to cure some ills but not a complete rebuild.
I’m under the assumption that its age and worn bearings are overbearing the regulator’s ability to maintain hot oil pressure to the FSM spec’d 44-50psi at 2.4k rpms. (FSM is not clear on any idle psi spec) Redline is emphatic about pressure at 2k+ rpms in terms of failure prevention but this rig will spend a lot more time below those spin rates. Thoughts?
I don't know, 5 psi at idle for a fully warmed engine running 10w-30 sounds decent to me. Sounds like a good plan to get all the pressure you can from the regulator and then call it good. I have a very strong F in my swb and I get around 20psi at idle with a fully warm engine running 10w-40.
The additional adjustment really only raised the cold startup pressure, so I’m going to set that to be at 50psi at cold idle as best I can. I still might pull the regulator and fully check it out when the Redline kit arrives.
You can spend a lifetime reading the endless debates on oil viscosity on the internet and since I only have one lifetime (here anyhow) I’m moving on . Since this engine is ubber worn (but not burning oil after my partial rebuild) I’m going to ensure that it’s boundary lubrication (see article below) function is at its best it can be given that that is the condition it will spend most of the rest of its life in. So I’m going to stick with 30wt (for better piston/ring cooling) per the FSM and the Operators Manual (10w30 is stated as appropriate substitute) and use the highest zddp one I can find. As best I can find thats Rotella T4 in dino based. And change it out frequently, which for how often I drive the rig that’s probably once a year (2-3k miles). Good to go, until I overthink this some more .
Understand Hydrodynamic Lubrication (HL) and Boundary Lubrication (BL)
The rod, crankshaft, and camshaft bearings aren’t sealed. The oil pump supplies pressurized oil to the bearing and that same oil constantly squirts out the sides of the bearings as the crankshaft or camshaft spin. As long as the oil pump can supply fresh oil at the right pressure at a faster rate than the oil leaks out, you’ll have Hydrodynamic Lubrication. In other words, the crankshaft, camshaft, rods, rockers, pushrods, etc will operate on a cushion of pressurized oil.
However, if you’ve neglected maintenance and the bearing surfaces wear to the point where the oil pump can’t pump enough oil at the right pressure to maintain oil pressure in those clearances, you wind up with Boundary Lubrication. At that point, the oil’s anti-wear additives are the only thing preventing metal-to-metal destruction. In older oil formulations, Zinc dithiophosphates (ZDP) or zinc dialkyl dithiophosphates (ZDDP) were used as the anti-wear additives. When the engine loses HL, and metal-to-metal contact begins, the ZDP and ZDDP additives melt out of suspension and act as a sacrificial lubricant. Loss of HL can happen on a cold start before the oil has a chance to build volume and pressure, or on a warm engine that has excessive bearing clearances and can’t maintain proper oil pressure. Those are the only times these additives come into play. The irony is that in a neglected vehicle, those anti-wear additives are likely already used up due to the extended drain intervals.