Results 1 to 8 of 8

Thread: SBC oil pressure is erratic

  1. #1
    Join Date
    Feb 2003
    Location
    Lacombe, AB
    Posts
    1,705

    Default SBC oil pressure is erratic

    The motor is a 406 SBC and has been on the street for a number of summers now, not a fresh build. It's a factory block, Dart iron heads, hydraulic flat tappet cam, eagle rotating assembly, nothing special. I drove it to work last week (about 15 minutes of 3000rpm on the hiway) and I didn't notice any issue going to work but on the way home the oil pressure kept dropping down to around 20 psi by the time I got home.
    Yesterday I took it downtown with no issue but it was a short drive. Last night I went to a buddies house and again, while it was cold going there the oil pressure was fine (it's around 80psi when cold and got down to around 60 by the time I got there). On the way home though as it warmed up it dropped below 20 and didn't seem to change much when I put it in neutral and revved it but then would jump back to 60 and then slowly drop again. The drive was only 5 minutes from my buddies and I was only a couple blocks from home when it started acting up.
    The gauge is a Speedhut with electric sender.
    I haven't changed the oil yet this year but only put about 1100km on it last year. Oil is Shell Rotella diesel oil, 15-40 and a Fram HP4 filter.
    I'm worried that I may have spun a bearing here. Any other suggestions/ideas? If no better ideas I'll be pulling the pan tonight to see what I find, as well as cutting open the filter.


    Canada - just like the U.S. only we pay twice as much or get half as much.

  2. Default

    I would try a different sender to start with, before I start worrying too much, or put a temporary positive gauge in to double check if oil pressure is fluctuating on both gauges.

  3. #3
    Join Date
    Nov 2007
    Location
    Edmonton
    Posts
    792

    Default

    With Roddychop on this one. Always nice to verify with a mechanical gauge. It's super uncommon but the symptoms sound like a loose pickup tube.

    Can you pull the filter and cut it to look for debris?

  4. #4
    Join Date
    Feb 2003
    Location
    Lacombe, AB
    Posts
    1,705

    Default

    I haven't done anything yet. I ordered an OTC oil/tranny pressure gauge that should be here Wednesday and then I'll check it out. If it's proven to be wonky with the mechanical gauge then I'll pull the filter and open it up. If it's clean I'll look at the pickup like you mentioned, if it's got metal I'll be looking at the bearings.


    Canada - just like the U.S. only we pay twice as much or get half as much.

  5. Default

    That sounds like a good order of troubleshooting.

  6. #6
    Join Date
    Nov 2007
    Location
    Edmonton
    Posts
    792

    Default

    I think you've got a good handle on this. Hopefully it's something simple.

  7. Default

    I agree with the checks you are planning and cutting the filter is always your easiest check for damage - but there is a way to determine if the pump pick-up is the problem without pulling the pan. If you add an extra 2-3 litres of oil it will raise the oil level up to the pump body inlet, then run the engine and see if the problem goes away - just don't drive it around or rev it too much as your crank will be thrashing through that extra oil. Also, if you are running the Rotella diesel oil to help protect the flat tappet camshaft, just know that if it is an API CI4/CJ4 rating the zinc additives have been mostly removed to protect the emission devices put on diesel engines since 2007. Hope you get a good resolution.
    Tom
    Last edited by engine_prof; 04-11-2017 at 10:39 PM. Reason: wording change

  8. Default

    I would also ditch that Fram junk filter - I had a bit of a different issue on a big block, would start motor and everything fine, 60-80psi, rev the motor a bit, then lose oil pressure and it wouldn't come back (stayed around 20psi), this was with a mechanical gauge. Changed out to a WIX filter and problem solved, and never an issue again. You can get WIX from AutoValue or NAPA (The NAPA Gold is the same as a WIX - just another number added to the part number). It may not fix your issue, but it won't hurt.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •