Chevy oil pressure

Just hooked up my new gauge. 60 psi cold idle, 45 psi warm. Sound good? I think it's great, but I can't find the operating range anywhere...

 

sounds reasonable

 

My 4.3 runs about 50-55 cold idle and about 20-25 hot.

 

oh, sure............ take the words out of my mouth

 

45 at idle is more than sufficient. I usually only worry with a small block chevy if the oil pressure warm is lower than 15 psi. Dont get me wrong that is not ideal , but minimally sufficient

 

I figured I was in good shape. Thanks guys!

 

I'm going to get a head start running away from the computer....

I know of a reputable engine builder who will tell anyone that 3 PSI (yes 3) at idle is sufficient to keep your engine alive. I think his point is that the pressure at idle isn't as important as the pressure at higher speeds. I think 15 PSI at idle is plenty. I think my Chevy had 15-20 at idle when hot.

 

As I see it, you have two ways that you can read low pressure. The pressure comes from the difference of the rate of delivery (the oil pump) and the rate of leakdown (the bearings draining). As long as there is positive pressure, there has to be oil in the bearings. You can have low pressure either from the bearings being loose, or from the pump being worn. I'd guess if the oil film in the bearings is sufficiently thin (ie proper clearances) as long as you have some oil pressure, there will be no metal-to-metal contact. I'm guessing about the physics of the oil film - I'd assume that there is a critical oil film thickness that will resist the force of the piston firing. Certainly the oil pressure will be irrelevant during the power stroke, because the pressure of the rod on the crank will way exceed the oil pressure.

So, I'd think low oil pressure would be ok if it's just the pump that's insufficient. I've heard of AMC 360s that have run for a long time with no indicated OP at hot idle - I'd assume that those engines have low OP because of pump wear, not bearing wear.

 

Growing up in the 60s and 70s and starting to find out about such things I always wanted at least 60 and would be happy if I could have got a 100 # of oil pressure. I imagine my disconsternation when I buy a new GM pickup with the then new throttle body fuel injection and it has 45# at higher rpm and bareley 20# at idle. The service manager who was a friend explained that it was something that auto manufactorers learned from Jap cars and the aluminum blocks they have. Seems that all those years we've washing our bearings out by keeping the oil pressures high. Seems that high volume pumps and not really high pressure pumps were the way to go. He said that the manufactorers found that less than 10# was needed at idle and 10# per 1000 rpm were all thatwere needed. Now I didn't know if this was so but I put more than 200K on that truck and owned several others that I put like miles on them. I remember in the old days seemed like we were always putting rings and inserts and bearings after about 60 to 80K. Maybe something to it.