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oil pressure question

Discussion in 'Trucks and Trailers' started by lawnandplow42, Mar 28, 2005.

  1. lawnandplow42

    lawnandplow42 LawnSite Senior Member
    Messages: 508

    On my 1987 Chevy with a 305 V8, the oil pressure is between 35 and 40 when the engine is cold. When it gets up to running temperature, it drops to just above 20. This seems low. How bad is this? Besides that, the engine runs and idles great. I keep up on the oil changes. thanks-dave
  2. grass_cuttin_fool

    grass_cuttin_fool LawnSite Gold Member
    Messages: 3,526

    I have an 85 that is the same way, an engine builder told me long as you have 1lb per 100rpms you are fine. So as long as you have around 5-7 psi idleing you should be ok
  3. riches139

    riches139 LawnSite Senior Member
    Messages: 369

    Normal. My 85 van was the same.
  4. lawnandplow42

    lawnandplow42 LawnSite Senior Member
    Messages: 508

    thanks a lot guys.
  5. jim dailey

    jim dailey LawnSite Senior Member
    Messages: 614

    Here is the Skinny. I had an '86 Silverado 4x4 short bed...305H motor. Bought it new. I put 386K miles on it over the years. My friend has it now and it just went over 500K. The bottom end of the motor has never been touched The oil is changed once every 4 weeks, with filter, of course. Straight old 30W is used. Oil pressure has always been at 30 psi under load, and 15-20 psi at idle. That truck has plowed snow and pulled trailers it's whole life...with no problems. The psi of the oil is not as important as the volume of the oil. Any GOOD mechanic or race car driver will tell you that. A million lbs. of oil pressure is nothing. It is the volume that counts. Also, that truck has the 700R4 tranny. The fluid and filter gets changed every 6 months. Never had any problems with that, and that is one of the least favorite of the GM trannies. CLEAN and VOLUME is the name of the game...not so much PSI.
  6. MJLsLawnCareNmoreLLC

    MJLsLawnCareNmoreLLC LawnSite Senior Member
    Messages: 840

    After an engine warms up the oil pressure drops. 20 psi is fine for oil pressure.

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