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Old 03-12-2009, 07:51 AM
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chevy 350 low oil pressure whats the deal?

well i start the motor and i get 40 psi i drive for about 20 min and pressure just keeps dropping i drive for a hour stop a light i look im getting 5-3 psi some times 10 i have to stay on the gas to keep pressure to keep it up! im running 10 w 30 new oil,new filiter? whats the deal
the filter im using is mobil 1

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Old 03-12-2009, 10:14 AM
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Quote:
Originally Posted by chevy bb 572
well i start the motor and i get 40 psi i drive for about 20 min and pressure just keeps dropping i drive for a hour stop a light i look im getting 5-3 psi i have to stay on the gass to keep pressure to keep it up! im running 10 w 30 new oil,new filite? whats the deal
Did you change the oil? Is there metal in it? Last time I saw this it was a spun bearing on the crank. Not pretty.
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Old 03-12-2009, 10:27 AM
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no metal in the oil i have changed the oil im thinking about using a compression gauge to check???
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Old 03-12-2009, 10:38 AM
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A compression gauge isn't going to tell you anything about the condition of the bearings and oil pump, just so you know. Did it have oil pressure before you changed the oil? Is this a manual gauge, or electric? Sending unit could be bad. How many miles on the engine? How's it used? Do the lifters clack when the gauge indicates low oil pressure?
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Old 03-12-2009, 10:38 AM
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oil

fram filter???
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Old 03-12-2009, 11:19 AM
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There are times that just putting a new oil pump has made a difference. I had a tired 350, 1psi at hot idle, put in a new hi volume hi pressure pump and it went up to about 30 hot idle. It is worth a try. If your looking for a cheap fix.
Dave
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Old 03-12-2009, 11:32 AM
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Quote:
Originally Posted by chevy bb 572
well i start the motor and i get 40 psi i drive for about 20 min and pressure just keeps dropping i drive for a hour stop a light i look im getting 5-3 psi some times 10 i have to stay on the gas to keep pressure to keep it up! im running 10 w 30 new oil,new filiter? whats the deal
the filter im using is mobil 1
How old? Generally low oil pressure is an indicator of:

- Leak between pick up and the pump.

- A filter failure

- internal pump leak

- relief valve hung open

- excessive bearing clearance

Change to a heavier straight weight oil say 40 or 50, if the pressure comes up everywhere, it's probably a leak that's internal to the pump, a filter failure, the relief valve hung up, or excessive bearing clearance. If the pressure stays the same or falls further it's a leak on the pick up side of the pump.

Bogie
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Old 03-12-2009, 01:27 PM
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Quote:
Originally Posted by flynbrian48
A compression gauge isn't going to tell you anything about the condition of the bearings and oil pump, just so you know. Did it have oil pressure before you changed the oil? Is this a manual gauge, or electric? Sending unit could be bad. How many miles on the engine? How's it used? Do the lifters clack when the gauge indicates low oil pressure?
i pulled the motor out of a 76 chevy monte carlo it had a dummie light that i checked it worked well i put a mann gauge on" brand new "i dont know for sure how many miles on motor the motor is used as a cruizer no lifter noises no chand in anything when pressure is down. i took car for a ride again and pressure rises when i hit the gas but drops @ idle when in gear below 10 in park it sits about 19-20
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Old 03-12-2009, 01:31 PM
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Quote:
Originally Posted by wildman1932
There are times that just putting a new oil pump has made a difference. I had a tired 350, 1psi at hot idle, put in a new hi volume hi pressure pump and it went up to about 30 hot idle. It is worth a try. If your looking for a cheap fix.
Dave
Daves Hot Rod Shop KC Mo
thanx i might try that
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Old 03-12-2009, 06:37 PM
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Most times this is a bearing leakage problem. Good OP at idle cold and poor at warm temps. What was the bearing clearances at when the engine was built?Rods and mains.
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Old 03-12-2009, 07:01 PM
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i never rebuilt the motor i just pulled slaped new gaskets on installed crusied
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Old 11-28-2010, 11:47 AM
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The high volume oil pump will most likely fix your problem, but if you do that you need to get a bigger oil pan, because the high volume pump will suck the standard size sump dry and then you'll lose all oil pressure until the oil comes back down.
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Old 11-28-2010, 12:44 PM
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Had the same problem with my 84 Camaro. Changed the oil pressure sender, problem went away. Only cost like 10 bucks, cheaper than an oil pump, and you don't have to drop the pan. If the sender is as old as the motor it's not a bad idea anyways.
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Old 11-29-2010, 09:03 AM
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Quote:
Originally Posted by chevy bb 572
well i start the motor and i get 40 psi i drive for about 20 min and pressure just keeps dropping i drive for a hour stop a light i look im getting 5-3 psi some times 10 i have to stay on the gas to keep pressure to keep it up! im running 10 w 30 new oil,new filiter? whats the deal
the filter im using is mobil 1
Do yourself a little favor. Try to replace the distributor with another if everything you have done failed. The distrbutor may not be sealing causing a leak down.
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Old 11-29-2010, 09:40 AM
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Quote:
Originally Posted by Red1993GMCSierra
The high volume oil pump will most likely fix your problem, but if you do that you need to get a bigger oil pan, because the high volume pump will suck the standard size sump dry and then you'll lose all oil pressure until the oil comes back down.
Slapping a high volume pump would be a band aide, if the pump is shot, sure, replace it, if you had a spun bearing you'd know it. If it's has big miles, bearings could be worn, and a freshen in order.

If it just happened overnight with no ill effects, check the external obvious issues, bad gauge, new or not, faulty sending unit, bad oil filter, low oil level.
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