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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: CashpitC10 on November 20, 2019, 01:48:38 PM

Title: ENG OIL PRESSURE
Post by: CashpitC10 on November 20, 2019, 01:48:38 PM

Have 83c10 with a 305 just changed oil less than a month ago. When i stop at a red light or stop sign the oil pressure drops below 20lbs. What could be the cause of this? Any help would be great.    Thanks Jody

Title: Re: ENG OIL PRESSURE
Post by: bd on November 20, 2019, 02:08:06 PM

Have you checked the oil level?  How many miles on the engine?  What's the oil pressure at 1,500+ RPM?  Was there a sudden decrease in oil pressure at idle or has it been this way for some time?  Have you verified the oil pressure using a manual test gauge or are you relying on the factory dash gauge?

Title: Re: ENG OIL PRESSURE
Post by: Shifty on November 20, 2019, 04:06:19 PM

The olde small-block Chevy formula was 10 pounds per 1,000 rpm, if that means anything to ya.

Title: Re: ENG OIL PRESSURE
Post by: bedwards on November 20, 2019, 06:54:49 PM

If your talking factory gauge, they are notoriously inaccurate.

Title: Re: ENG OIL PRESSURE
Post by: Shifty on November 21, 2019, 08:33:48 AM

Quote from: bedwards on November 20, 2019, 06:54:49 PM

If your talking factory gauge, they are notoriously inaccurate.

Agreed.  According to mine, I should be pushing the truck instead of driving.  :o

Title: Re: ENG OIL PRESSURE
Post by: JohnnyPopper on November 22, 2019, 01:29:07 PM

Are you using a multi viscousity oil, like 10-30?

Might be too light for a truck with high mileage.

Could go with a single vis oil, or move up to 20-50.

You don't hear knocking or rattle when that happens do you?