Q&A / Tech

Mailbag: Diagnosing Insufficient Oil Pressure & Oil Starvation

 

Q: I have a 1985 Camaro Z/28 with the 305 TPI in it. When I was just cruising around, I glanced at my oil pressure gauge. One minute it was normal, the next it registered zero! As I was driving home, I noticed the gauge would register 5 psi at around 3,500 rpm, so I knew it wasn’t the sending unit.

When I got home, I removed a valve cover and found out I was getting no oil to the valvetrain. I removed the oil pan to check the oil pump, and it looked fine. Needless to say, I’m stumped.

If I can’t solve the problem, I was wondering if I could swap in a 350 short block and use the 305’s TPI setup.

A: The oil pressure problem is a bit of a mystery, but we have a few things you may want to check for:

  • A restriction in the oil pickup tube
  • An open oil pump bypass spring
  • A loose oil pump bolt between the pump and main cap
  • A loose or missing oil gallery plug
  • Low oil level (obvious, but did you check?)

If you do decide to swap in a 350 short block, you should use fuel injectors from a 350 TPI setup to prevent a lean condition. You can use an older short block as long as you keep the cam timing reasonable, around 208/214 degrees of duration at .050-inch lift and .450-inch valve lift.

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5 Comments

  1. I have seen worn cam bearings do just that.

  2. Freshly rebuilt 350 Olds Rocket. Followed cam break in procedures used recommended oil and additive.Oil was changed after break in.
    At the 400k mark the knocking was noticed on the return from a 150k cruise. tear down revealed 3 cam lobes with extreme wear and the #8 rod bearing almost totally gone. Mains showed signs of wear. What Took this engine out?

  3. Had this issue on a small block Chevy. Builder didn’t get the rear cam bearing all the way in place. Oil was going straight from the rear cam bearing back into the pan.

  4. Kyle Meeks says:

    I had the 4.3 LS in my work truck lose oil pressure randomly. Had it towed home and tore it apart. Changed pressure switch, nothing. Pulled oil pan and everything looked fine. Pulled the front cover and oil pump, bingo. The bypass valve had a burr on it and was stuck open.

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