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| | | | Joined: Feb 2014 Posts: 125 Shop Shark | | Shop Shark Joined: Feb 2014 Posts: 125 | Can someone tell me what the oil pressure should be on a 1975 Chev 250 CI in line Six. | | | | | Joined: Feb 2004 Posts: 29,881 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,881 | Oil pressure will vary according to temperature, bearing wear, and the viscosity of the oil. A good-condition engine running 10W-30 oil will probably start out cold at around 40-50 PSI and drop to 20 PSI or so at hot idle. The switch that turns on the idiot light oil pressure warning contacts at about 7 PSI, so a lot of people who don't run an accurate gauge have no clue how low the pressure actually is at times. "The light's out, it must be OK, right?"
Actually, it's theoretically possible to lubricate an engine with zero oil pressure- - - -as long as all the bearings receive oil at exactly the rate it's being leaked away back into the crankcase, the pressure on the gauge will be zero. Any oil pressure at all indicates the engine is getting more oil than it needs.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Feb 2014 Posts: 125 Shop Shark | | Shop Shark Joined: Feb 2014 Posts: 125 | Thanks jerry. This engine is in my 53 so the original gauge and no idiot light. Pressure is around 28 to 30 PSI when on the road. I can now assume all is well. | | | | | Joined: Jan 2016 Posts: 631 'Bolter | | 'Bolter Joined: Jan 2016 Posts: 631 | There is an old rule of thumb:
10psi for every 1000 rpm as the minimum. ( hot engine) ( modern full pressure system not a 216)
Example
1000 rpm = 10 psi
3000 rpm = 30 psi
These are minimum values, obviously 10w vs 30w would make some differences. But if the engine does not meet these minimum value start looking for issues.
Last edited by showkey; 03/26/2016 4:51 PM.
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