Big block oil psi

[Mark B.]

I was curious, I have 69 corvette L36, what type oil psi should I be seeing?

[Mathew S.]

Re: Big block oil psi

My 1970 LS5 runs close to 70'when cold or above idle, and warmed up runs around 35 psi when warm. I'm running the Joe Gibbs Driven Hot Rod oil, I think it's 10w40.

[Joe R.]

Re: Big block oil psi

Mark,

There is no way someone can give you the correct oil pressure for your engine, BB or SB.
Oil pressure is dependent on several factors including oil pump. oil viscosity and bearing clearance on both rods, camshaft and mains. Bearing clearance is determined by your engine builder.

JR

[Mark E.]

Re: Big block oil psi

As a data point, stock 1970 LS5 (basically the stroked version of your L36, but don't know if the pump setting is the same) running Mobil 1 15W-50:

- At the hash mark between 35 and 70 (about 50-55 psi) when cold and above idle speed. I suspect this is the pump's max pressure setting.

- A bit below the hash mark (45-50 psi) above idle speed and at operating temperature

- 35+- psi @ 700rpm and at operating temperature

I recall it ran a bit above the lower hash mark between 0 and 35 (about 20-25 psi) @ 700rpm, operating temp. with Mobil 1 0W-40.

These are gauge readings; I've never checked its accuracy.

[Mark B.]

Re: Big block oil psi

Thanks everyone for the replies, I just got this car and will be changing the oil, I am going to use the Rotella T 15-40w oil. Also i need to change the oil psi gauge as I have the white face and want to change to the original On cold start, I am about 40-45 psi

[Duke W.]

Re: Big block oil psi

Download the '69 Corvette vehicle information pdf from the GM Heritage Web site. IIRC the specified HOT oil pressure for all big blocks is 55-70 psi at 2000 RPM. GM does not specify idle pressure, hot or cold or cold oil pressure at any speed, but typical idle pressure depending on idle speed will usually be between about 15-35 psi, hot. Because the oil pump is a constant volume type, higher idle speed means higher oil pressure, and oil pressure at just about all engine speeds will be higher when the oil is cold than hot.

From idle speed, hot pressure should increase and max out in the 55-70 psi range and not increase further above about 2000. That's when the bypass valve begins to open. Oil pressure is engine speed dependent regardless of load.

Duke

[Mark B.]

Re: Big block oil psi

Thanks so much