So I noticed once car warms up I have like no oil pressure at idle and when driving it will go as far as half. Let off gas it drops to red zone..... Is this bad on these cars?! Ideas of why this could be?

 

No oil pressure is bad on any car. However, old pressure sensors can cause low readings. You might want to verify pressure with a mechanical gauge.

 

Mine is 18 at idle once warmed up. Seems the norm on these older cars with over 100,000 miles. When you say no pressure, how low does it goe?

 

It's like at the red at idle and sending unit is brand new. Only when warmed up though cold start its at about 15-20

It's not at 0 pressure shoebox it's at the top red mark not the 0 one

 

What viscosity oil are you running?

 

You're only required to have 10psi @ 1000rpm
What is your car idling at ?? in gear with my foot on the brake my car will dip
down to 800rpm's
15- 20 on a cold start does seem to be a little low ... I would look in to what shoebox suggested and answer Freds question ...

 

Having the same issues... Without new sending unit.
Have heard of the gauges and sensors being garbage, but why would it be okay cold?
Running the suggested 5w30.

 

Oil is thicker when it is cold. Hence, the pressure is higher. The sensors and gauges aren't garbage. Just like anything else on the car, they age (mostly the sensor).

 

I have an AutoMeter mechanical oil pressure gauge, and it matches the stocker readings. Where did you hear the gauges and sensors are "garbage"????????

 

This is nice to have, but you'll never see it with a stock LT1. According to GM as long as you have at least 6 psi at 1000 rpm 18 at 2000 rpm and 26 at 4000 rpm you're good to go.

Although I wouldn't be comfortable with pressure that low, the engine will live on it.

 

Yes they will live on that low of oil pressure. I had a 4.8 that lived for several 100k miles and years at about that level of oil pressure. It actually never did die. It was running at 535k miles when I finally got tired of waiting for it to give up the ghost. This was in a express van that saw lots of stop and go driving by people who didn't own it meaning it was beat on.

 

It may "live" with 6psi at idle, but unless I've misunderstood you(and I may have....), your first sentence is just wrong. Those pressures are minimum, but not normal by any means. There is a problem brewing with a motor that presents with low oil pressure.

A stock LT1 with everything within factory tolerances(bearings, crank, etc) will idle with a hot oil pressure of 18-20psi. A cold start should present pressures above 45psi. Stock crank bearing clearances are under 0.002". Rods are a little looser....around 0.0025"-0.003"(IIRC need to double check).

My cold start pressure is above 65psi and I have bearing tolerances that are slightly looser than stock. My hot idle pressure is 25-30psi. I also have a higher pressure spring installed. Before, when it was stock, I tore this thing apart at 95,000 miles for my cam, bearing refresh, roller rockers, etc it had hot idle pressures of 25-30psi and maxed out at 50psi@5700rpm.

Unless there is an electrical or sensor issue, there is nothing mysterious about oil pressure issues. Loose bearing tolerances(cam, crank, or rod) somewhere in the engine "generally" account for oil pressure anomalies.

From my understanding, SBC gen 1 and 2 oil pumps generally just don't fail. They are rock solid reliable.

The only other real issue on oil pressures I've seen is if the pickup falls off the pump. However it is generally okay at idle, that presents itself with oil pressure falling when braking....and I guess I can't forget to mention that no oil pressure issues can result from the oil pressure drive gear or stock plastic coupler having problems.

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The 2:30min mark for hot oil pressure readings(high pressure spring). Normal pressure springs will generally top out around 50psi hot(IIRC), however the normal hot idle should be 18-20psi.

 

I'm with you Eric... you can and should see reasonably high oil pressures on a stock (and healthy) LT1. I bought mine new, and from the day I bought it new, until 6 years and 60,000 miles later (pulled to build the stroker) it showed 40+psi on cold start and 30psi at warm idle (800 actual RPM with the M6). Would climb to 60psi directly proportional to RPM. And that's with the factory spec'd 5W-30.

 

I'm getting pretty much the same pressure as Fred and Eric reported on my stock 95 with 220k miles. 45psi cold start, 20-25psi warm idle (800 RPM), and at least 50 at high RPM.