Timing and oil pressure

Discussion in 'Troubleshooting & Diagnosis' started by phantom69, May 6, 2021.

  1. phantom69

    phantom69 Member

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    im trying to figure out what the potential issue is concerning my carbureted big block and the oil pressure..im not sure if this is the case but does retarding the timing decrease the oil pressure thruout the rpm range?
     
  2. Rosster

    Rosster Veteran Member Gold Member

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    No. Oil pressure is a function of the oil pump speed which is dictated by engine rpm. If rpm is low (idle), pump output can drop causing lower oil pressure. As you increase rpm, output is usually sufficient to increase pressure up to the point the relief opens. If you are seeing decreasing oil pressure over time, you may have bearing issues.
     
  3. mallard

    mallard Veteran Member

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    ^^^^^^^^^^ what he said. Only way "timing" affects oil pressure is possibly indirectly at idle because the retarded timing makes your idle to low.
     
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  4. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    ^ Correct.
    Oil viscosity will change with temperature and reduce oil pressure at higher temps but timing has no effect on the pump function.

    If the car is running too hot due to retarded timing, there may be some drop in pressure due to oil thinning at the higher temp.
    (Pressure normally drops after the engine is warm but the oil pressure difference between "warm" (180*) and "hot" (230*) won't be much.)

    What weight oil are you using and what oil pressure are you seeing at cold startup and after it's at operating temp?
     
  5. phantom69

    phantom69 Member

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    ive got mostly royal 10w-30 and maybe a quart of 20w-50 with some honey treatment..i did change to taller valve valve covers couple months ago think might also be a cause..will be switching back to the original shorties on there that are more compressed on the block..i idle at about 700rpm usually and oil pressure usually at 5-6..rev it up to about 2500rpm dont get above 18psi..this was immediately after a trip to the shop it is noticeable after accelerating from a stop dont feel like enuff oil is circulating
     
  6. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

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    Tall valve covers won't change oil pressure.
     
  7. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    If your oil pressure is at 5-6psi at idle and only 18psi above 2500rpm you've got excessive bearing clearances or a failing oil pump

    Have you checked oil pressure with another gauge to confirm those #'s
     
  8. muscl car

    muscl car Veteran Member Lifetime Gold Member

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    Fuel soaked oil from a bad fuel pump or leaking carburetor can and will thin the oil down resulting in lower oil pressure
     
  9. phantom69

    phantom69 Member

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    fuel pump is good only couple months old edelbrock victor series..carb is the performer 750 again few months old..the only thing i can think of is the suggestion you made of bearing clearances or maybe oil pump..i wanna see if other things might be the case or other methods to fix the issue
     
  10. mallard

    mallard Veteran Member

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    Just out of curiosity, what is your oil pressure reading?
     

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