low oil psi

dastang2

Active Member

Dec 11, 2003

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tx

Mar 7, 2007

#1

• Mar 7, 2007

• #1

i put a good crank and new bearings on the lower end with a known good high mileage oil pump on the motor. i did nothing to the cam bearings. the car had 50 psi when cold and 25 when hot at idle for a few months but i let the car sit for a month and now i get 30 cold and around 0 hot. does this sound like an oil pump or cam bearings. the oil psi goes to 40 when driving now. the oil is good and clean but feels really thin. not sure if it has 10w30 or 40 in it. i also have no gasket between the pump and block, i was told by many on here, that is not needed

 

8

86bluecobra

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Dec 20, 2004

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Mar 7, 2007

#2

• Mar 7, 2007

• #2

I don't have a gasket myself either. (between the oil pump and block) Perhaps though thats where you should start. If the 2 surfaces are not machined perfectally it could be your problem. A gasket will take up the slack so to speak. It is wierd that after it sat it got worse. Is it a carb'd engine? Does your oil smell like gas? Is it possible the carb/injector bled down the fuel psi into a cylinder and into the oil? This would break down the oil and cause you to lose pressure. Why did you replace crank and bearings? Did you plastic gauge the bearings/ crank for clearences?

 

8

86bluecobra

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Dec 20, 2004

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Mar 7, 2007

#3

• Mar 7, 2007

• #3

I found the old thread you were talking about. that was over a year ago. So your car had good oil pressure for a year?

 

V

v8only

Active Member

Jul 3, 2003

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Mar 7, 2007

#4

• Mar 7, 2007

• #4

a known good high mileage oil pump? christ guy they only cost $20, 1 vote for the oil pump here.

 

Aryan15

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Sep 22, 2003

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CA

Mar 8, 2007

#5

• Mar 8, 2007

• #5

Oil pressure sending unit?

 

dastang2

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Dec 11, 2003

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tx

Mar 8, 2007

#6

• Mar 8, 2007

• #6

mech. gauge and i know i should have put a new one in. i haven't driven the car much because it is not legal yet. just around the neiborhood and such and not very long. it was making good psi when i put it together and when i let it sit. then i cranked it and noticed the oil pressure was way down. the oil does feel a little thin and i smelled it, it smelled like oil but may have had a hint of fuel smell to it. i have a DP 650 that probably need to be rebuilt.

 

dastang2

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Dec 11, 2003

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Mar 8, 2007

#7

• Mar 8, 2007

• #7

86bluecobra said:

I don't have a gasket myself either. (between the oil pump and block) Perhaps though thats where you should start. If the 2 surfaces are not machined perfectally it could be your problem. A gasket will take up the slack so to speak. It is wierd that after it sat it got worse. Is it a carb'd engine? Does your oil smell like gas? Is it possible the carb/injector bled down the fuel psi into a cylinder and into the oil? This would break down the oil and cause you to lose pressure. Why did you replace crank and bearings? Did you plastic gauge the bearings/ crank for clearences?

Click to expand...

here is the story. i had this good crank and bearings in another block that i never cranked up. i plastigauged the bearings in that motor and they were within spec. when i swapped the parts to this motor, i did not plastigauge because i couldn't find any plastigauge and the parts place was a long ways away. i got too eager.

 

8

86bluecobra

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Dec 20, 2004

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Mar 8, 2007

#8

• Mar 8, 2007

• #8

well one should never get to eager. I do know the feeling though. I'm sure its not a main bearing issue however. If the old block with standard rngs was ok then i'm sure this one is. But ............ well i don't need to tell you what you should have done. Oil pumps usally pump or don't pump. They a gear design. That being said they can get weak due to wear over time. Am I correct in thinking that you installed a tubular k-member in your car? If so it should be fairly easy to remove the pan and install a new oil pump and gasket.

 

bullitstang1313

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Jan 21, 2003

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Indianapolis / Columbus, Indiana

Mar 8, 2007

#9

• Mar 8, 2007

• #9

How long did the engine sit? Oil can begin to breakdown over time. I wouldn't think it is the pump or you would probably not have pressure any time.

 

8

86bluecobra

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Dec 20, 2004

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Mar 8, 2007

#10

• Mar 8, 2007

• #10

bullitstang1313 said:

How long did the engine sit? Oil can begin to breakdown over time. I wouldn't think it is the pump or you would probably not have pressure any time.

Click to expand...

I have seen oil pumps loose all pressure for periods and then pump again. But i do agree with you on how they typically die. Thats why I asked if his oil smelled like gasoline to see if thats what broke down his oil.

 

dastang2

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Dec 11, 2003

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tx

Mar 8, 2007

#11

• Mar 8, 2007

• #11

i guess i didn't smeel how much gas was in the oil because there was a lot, i changed it and i have my pressure back thanks.

 

8

86bluecobra

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Dec 20, 2004

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Mar 8, 2007

#12

• Mar 8, 2007

• #12

Sounds like you need to take your carb apart and clean it. A small piece of dirt can cause a carb to allow a bowl to leak its fuel into the engine.