Oil circulation/pressure problem

Discussion in 'Mech Tech' started by Pumpkin jack, Mar 24, 2019.

  1. Pump engages properly but pump itself is a very easy fit. Not loose by any means but definatley not tight. i will fit some tape around it ( as suggested on another thread )
    and see if it helps
  2. A loose pump could be the issue.
    With thin oil and a hot engine you get an air leak.

    On all three engine blocks I have used, it has been necessary to slacken the case bolts above and below the pump to be able to get it in and out even still needing a puller with bolts undone.

    In my parts boxes I am sure there are a few odd spare oil pumps.
    Even an unused CB Maxi 3 which is a full flow solution without drilling which still hits over 100 psi on a cold start.

    It might be easier to try another pump.
  3. Is it a proper type 4 pump ?
  4. Sadly it's going to be a strip down and rebuild. I spoke to a local bug mechanic and was told it is probably the main bearings. It's going to be costly but I'll take it out and let him do the work.
  5. Surely it's easier to try a better fitting pump first than split the case?
  6. Speaking to the mechanic, he pretty much summed up all the issues I had and various things I'd tried and said it was the only thing left to do.
    After spending the weekend taking pumps, coolers etc off only to loose even more start up pressure, I think he's right.
  7. it is a CB pump for a type 4, I swapped out the standard pump because of the oil pressure problem
  8. Why don’t you take it apart yourself? You won't learn anything or know what is really wrong giving it to someone else to fix.
  9. I'd love to...
    Unfortunately space to work cleanly in is limited and there's only so many times my wife will let me put the engine in the dish washer :)
    We've owned it for a year and a half , still need to finish the internals and basically just want to start using it, so time to delegate
    77 Westy likes this.
  10. Did you discover what the problem was?
  11. Yes. Gave the engine to a bug mechanic, he said case had been machined and I'd fitted the wrong sized bearings.
    He sorted it for me. Now engine runs okay although may need oil cooler fitted as I could hear what sounded like oil boiling after a long run. It was sitting steady between 89-98F the whole journey though.
  12. Good that you’ve found the problem; a bit basic though and you’ve spent a few quid buying bits you don’t need – I might be interested in the Tangerine Racing pressure relief valve if you want to sell it.

    I assume you mean 89-98C, that’s just right. If it’s deg F it’s far too cold.
    Valveandy and snotty like this.

  13. Just glad it's running now and I can use it. Yes, my mistake, cht temp is 89-98C
    Rises when in stationary traffic to 110+ and 140+ after switching off engine.
    Pressure relief valve is still in engine and hopefully doing its job.
    I found a decent idle jet set up for my Idf carbs, it's Starting to splutter a bit when pulling away but runs well enough. I will be fitting Bosch l jet system over the winter though
    77 Westy likes this.
  14. That’s very low CHT, where are you measuring the temp? I would expect normal CHT measured under the spark plug of around 350/375F (175/190C), lower at idle and after switching off, higher under heavy load.
    55 idle jets should be in the ball park – depending on the engine spec of course.
  15. Sensor is under #3 plug. Temp definitely rises in slow moving/stationary traffic.
    Idle jets are 52 and I went a size down on venturi (which made a huge difference) After covering 500 miles, plugs look clean.... but exhaust stinks, hence the bosch l jet this winter

    Sent from my EVA-L09 using Tapatalk
  16. There’s something not right with that CHT, either the sensor/gauge isn’t accurate or #3 isn’t firing. The engine would produce little or no power with 89-98C head temperatures. And the temperature should drop at idle (no load) and although there might be some heat soak it should fall as soon as the engine is switched off. Where is the connection between the sensor and the extension cable to the gauge – inside the engine bay or under the tin?

    Does the engine have a working thermostat and flaps?

    What size vents did you change from and to?
    snotty likes this.
  17. I have a CHT sensor in the Mexican temerature sender boss on my EMPI heads. It reads 80 to 90 degrees C running, maxing about 130 on switch off. Previously similar sensors with less insulation on them would read 110-150C in the same boss on my old engine. ( added electrical insulation because of earth loop problems )
  18. New type thermostat fitted. It works okay
    Venturi size is 34 image.jpeg
    Cht sender wire runs as shown image.jpeg

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