Oil pressure mechanical questions, 1989 Astro, 4.3 engine.

[ArtDecoWorld]

1989 Astro, 4.3 engine.

Hooked up a mechanical tester gauge. With the doghouse removed, it's easy to drive around with the gauge in your lap, since the engine is in the crew compartment. Results:

Warm idle is around 26 PSI
Driving around town is around 34 PSI
Driving at 65 on the highway is around 36 PSI

Only reference to oil pressure numbers the owner's manual makes is this:
"Readings of 30 to 40 psi may be considered normal during moderate road speeds of 35 to 40mph with the engine at proper operating temperature." (This despite the cluster gauge in my van having no numbers on it.)

I tested both with 5w-30 (the default in the manual) and 10w-30. I tried two different filters. I used two mechanical test gauges (both Harbor Freight). There were no appreciable differences. I was in the 30 to 40 PSI range during moderate speeds. But, should the other readings be different?

Thoughts?

 

[Trav]

Still well within the minimum, these old style pumps didn't make a lot of pressure even when new, your hot idle press is good. Unless you are having some issue I would forget it. If you wanted to it is easy enough to drop the pan and replace it with a Melling pump.

 

[GMBoy]

I agree with Trav - all looks fine to me. I worked at the Baltimore Plant that built that Van from 1987 thru its closure in 2005. I have a soft spot for those vans!

 

[Tman220]

Still well within the minimum, these old style pumps didn't make a lot of pressure even when new, your hot idle press is good. Unless you are having some issue I would forget it. If you wanted to it is easy enough to drop the pan and replace it with a Melling pump.

View attachment 92605

Yup that's been the spec from GM on any of the Gen 1 and Gen 2 SBC's, V8's and the 4.3 V6's. Knowing this is why it always bothers me whenever someone quotes the 10 psi per 1000 RPM line while referring to these engines, which is obviously misleading in this case.

If you got more than 20 psi at hot idle on these engines you are in darn good shape. An easy mod to do to the oil pump though is to install a higher pressure relief spring. The stock one is only good for like 45 psi and after 20 years and 100's of thousands of heat cycles it's likely less.

 

[ArtDecoWorld]

I very much appreciate the responses and information. Thank you.

My main concern was whether PSI in the 30's was ok/in spec for freeway driving.

 

[benjy]

in warmer climates oil thins, hotter is thinner as spec is at 100C above that its thinner! of course wear factors in which you dont mention, so a thicker oil may be an EZE fix + in california - north or south? a 10 W would be fine as well as heavier 30W.