Oil circulation/pressure problem

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

  1. Hi all.
    Thanks for the help with my cv joints......
    my engine oil light comes on when warmed up (70degrees + at idle,according to cylinder head sensor)and engine starts knocking. its a 1700 increased to 1911 with new barrels Pistons. Cylinder heads. It has scat 35 cam
    When I increase revs it disappears but returns at idle. I've tried various things....new CB performance 26mm oil pump (no outlet on cover). New pressure relief spring and piston.
    Cutting down and refitting fuel pump rod ( as recommended by Vwheritage) as I now have electric pump to run twin Webber Idf 44 carbs.
    Changed oil pressure switch twice. I have a pressure gauge but haven't fitted it yet
    It sounds like once pressure relief piston moves, oil doesn't get around the engine properly.
    I'm a bit concerned about going too far before doing untold damaged and don't fancy another strip down if possible
  2. You need to check the actual oil pressure. What oil are you using? Worn bearings are usually the main culprit.
    snotty likes this.
  3. Baysearcher

    Baysearcher [secret moderator]

    Knocking doesn’t sound good...
  4. Is this a recent rebuild?

    Was the CB pump a tight fit in the crankcase?

    Was the pressure relief piston a good fit? (I have two crankcases with different diameter pistons) And what about the pressure control valve by the pushrods, is that okay?

    You need to fit that pressure gauge.

    Not related to oil pressure but what vents and jets do you have in the Weber’s?
  5. Did you replace the big ends while it was apart ?
  6. Yes recent rebuild, new bearings new cam
    Case only has one pressure relief valve
    I will be fitting the gauge, just have to adapt tinware to take both fittings
    Not sure about vents but I've been going through different idle jets-5, 5.2, 5.5, 6.0
    But that's another issue:(
  7. I had an exchange middle block go down after 60 miles.... Mains bearings went apparently..... I would get that back to the people who built it..... knocking is never good, however the replacement that I received (same block re-worked!) didn't knock at all when that seized last month after only about 4k!!! So beware of the engine shop!
    Lasty likes this.
  8. Leave tinware and fit an extension hose..

    Clip our stock " red light" and gauge sensors onto the tinware at the back...[​IMG]

    Sent from my SM-G930F using Tapatalk
    Gooders, andyv and Pumpkin jack like this.
  9. A wrong sized oil filter will knock
  10. A late case then - would originally have been a 2.0l with hydraulic followers.

    CB Shadek pumps are often a loose fit and leak internally; do you know if the engine builder checked the fit?

    If the pressure had been okay I’d have said the knock was the cam with too much thrust clearance but if the oil light comes on the pressure is being lost somewhere. Check the pump first but you may have to split the case to investigate. It might have the wrong oil pickup; a late case needs the short pickup.

    You’ll have difficulty tuning the carbs, IMO 44’s are too big for a relatively small capacity engine and you can’t get vents small enough. 40 IDF’s with 28 vents would be better, unless you have high flowing heads with big valves.
  11. It was a USA import. I assumed it still had the original 1700 engine.... Cb07 code on fan housing. I did the rebuild myself. It didn't have hydraulic lifters but maybe that would help with oil flow? I have only just changed the pump from stock to try to increase pressure because of this problem and the new pump seemed to fit as well as the original. It does sound okay when cold. (No knocking) It did run without any problems when I had the bigger idle jets on the carbs and had just fitted a new oil sensor but the exhaust absolutely reeked, so I went down two sizes. Would this be linked??
    I only chose the scat35 cam to suit the carbs but yes they are too big for this engine.
    I've done various oil changes using sae30, 20/50 and now 15/40 with zinc additive
    It's only done 20 miles since rebuild because of cv joint probs
    I'll put the bigger idle jets back on just to see!
  12. Where is this available from??
  13. +1 for the oil extension hose. Think mine was from Demon Tweeks via ebay.

  14. The engine number is on the crankcase below the breather tower and hidden by the fan shroud, a CB engine would have been dual relief; single relief cases were much later – mine is a CJ.

    If the pump was a good fit you’d need to slacken the case split line bolts above and below the pump to fit it. The standard 24mm pump should have been fine but if the oil light comes on there is virtually no pressure so it must be going somewhere, I suppose the pump is engaged fully with the cam? Did you clearance the pump to avoid the cam bolts? Did you fit a new ‘o’ ring on the oil pickup pipe? You could try putting an extra ½ litre of oil in it, which may take the level above the pickup pipe.

    If the heads are 2.0l or 1700 bored out for bigger cylinders they’ll have small valves, a C35 cam has a lot of duration and lift (compared to a standard bus cam) and it’s not a good match for small valves and the huge carbs will make tuning difficult. I can’t remember what the smallest vents are for 44’s but I suggest you fit them. You’ve built a bug engine that won’t have much low down torque but it’ll like revs and should make reasonable bhp – if you can get the carbs dialled in. Incidentally, what compression ratio do you have?
    Majorhangover likes this.
  15. For oil pressure I just opened up the hole in the tin slightly and fitted a dual sender – simple.
    snotty likes this.
  16. ...then you start the whole dual senders and the false dash low pressure warning debate.....

    Sent from my SM-G930F using Tapatalk
  17. Mine has never given a false warning. :D
  18. I fitted a Durite 0-100psi gauge which works ok but not as accurate a VDO. When hot after a long run oil pressure on idle is as low as 10psi which is ok & not low enough to put the light on. Have heard 10psi per 1000rpm is about right when hot.
    Last edited: Mar 24, 2019

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