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Oil in the distributor - 48D4

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  • Oil in the distributor - 48D4

    I've been pulling my hair out - and it hurts. I have a 1.7 O Series engine in my Roadster and it has been giving good service until..... I changed the distributor to an electronic version of the 48D4. I used to get oil in the main body of the old distributor (replaced unit) but not that much. With the new distributor, I get the best part of half a teaspoon-full after 50 miles or so. The shaft fits snugly in the housing and there is an anti-splash washer on the base of the unit to stop excessive oil dripping on the shaft. The only way I can think oil is being forced along the shaft is if there is excessive pressure in the cam cover. I'm now moving out of my comfort zone. I understand that if the engine breathing system is faulty an increase in pressure is likely but how do I test for this situation? Likewise I was wondering if worn valves or piston rings might lead to excessive pressure in the cam cover. For those not familiar with the 48D4, it fits horizontally into a circular aperture in the cam cover and a gear on the end of the distributor shaft engages with a worm gear on the cam shaft. I do need to resolve this problem because build-up of burnt oil on the contacts in the distributor cap has resulted in my ignominious return home on the back of a recovery vehicle ; the only up-side to this story was that the recovery mechanic convinced me the problem was a failed fuel pump! What do they know ! Thanks in advance for your thoughts.

    Cheers Alan

  • #2
    Re: Oil in the distributor - 48D4

    I would check the engine breathers as these were quite a common fault with the O series. There were two types of oil filler one was on the cam cover & the other was on a metal tube on the side of the block,inside the lower section of this is a wire gauze which blocks up over time sometimes with carbonised oil but more often with emulsification.Remove the pipe/breather & clean with petrol (if solid i have burnt it out before now,but not with petrol just burn the oil & knock out the residue).Valve stem seals were also an issue you would only notice this if the engine had been idling (ie at traffic lights) & then when accelerating away you will get a cloud of smoke then it will clear.

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    • #3
      Re: Oil in the distributor - 48D4

      Best source I have found for distributor issues has been http://www.distributordoctor.com/

      Not the cheapest but quite probably the best in the field.

      I'm guessing there is a seal on the distributor shaft that has failed.
      It could be possible that your rocker box is becoming pressurised, has the breather in your oil filler cap become blocked?
      MOC member since 05/97
      1984 Marlin Roadster SWB.
      1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
      Three core radiator, Renault Clio vented front discs.
      The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

      Loads of Marlin Reference can be found documents here or there.

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      • #4
        Re: Oil in the distributor - 48D4

        Thanks for your thoughts thus far. I do suspect that the engine might not be breathing properly but , how to I check the breathing? Are there some basic tests I can apply? My engine has a tube fitted to the lower block which has a rubber tube connecting the top of the tube to the SU carb. I can blow freely down the tube if that helps. I think that the cam cover is being pressurizes because, apart from oil in the distributor, I also have a pesky leak from the oil pump gasket which I have changed several times (inc the pump) and it still leaks. The distributor is brand new and does not have a seal in the shaft (that's the design). Does the oil filler cap feature as part of the breathing system. All thoughts welcome. Cheers

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        • #5
          Re: Oil in the distributor - 48D4

          I have been told there is no internal shaft seal on the dizzy so problems must be pressuriasation problems. This suggests that your piston rings/cylinder seal is not what it might be.

          However, if there is too much crankcase pressure, there should be other signs.
          You describe the breather from the side of the crankcase to the carb. The breather can become clogged, but it is easy to remove and check as you have found.
          It is possible to simply take the breather hose off the carb to check pressure - although the same is fairly obvious just by removing the oil filler cap while the engine is running, and check pressure by placing your hand over the opening.

          The problem with the breather arrangement is that it only operates effectively while the throttle is open.
          When the throttle is closed there is very little vacuum to remove oil vapour because the breather is outboard of the butterfly.

          Hope this helps.
          MOC member since 05/97
          1984 Marlin Roadster SWB.
          1800TC, Unleaded ported head, stage 2 cam. Ford Type 9 gearbox, Dolomite Sprint rear axle fitted with MGF disc brakes.
          Three core radiator, Renault Clio vented front discs.
          The reasonable man adapts himself to the world; the unreasonable one persists in trying to adapt the world to himself. Therefore all progress depends on the unreasonable man.

          Loads of Marlin Reference can be found documents here or there.

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          • #6
            Re: Oil in the distributor - 48D4

            Thanks very much for the info and your efforts to help. Tomorrow I'll dig out the overalls and do some testing. Do you know whether piston rings for the 1.7 engine are readily available should it come to that? I hope not!

            Cheers

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            • #7
              Re: Oil in the distributor - 48D4

              Be very surprised if you can't find some rings...try F W Thornton in Shrewsbury. They claim to be able to source almost anything
              Classic Engine Parts & Vintage Engine Parts From FW Thornton Worldwide Suppliers Of Pistons, Engine Bearings & Gaskets For Classic & Vintage Vehicles - Buy Online - For Expert Help & Advice Call Us On +44 (0)1952 246082


              Not sure if the oil filler cap is part of the breather system but close inspection should reveal if this is the case...if so give a thorough wash in paraffin/petrol to clean.
              Marlin Roadster, LWB...1860 B Series + Ford Type 9
              Renault Espace 54mm front calipers, vented discs, cycle wings and adjustable tie-bars.

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              • #8
                Re: Oil in the distributor - 48D4

                Now my dizzy has a little hole drilled in it to drain it. The 1.7 O series has the dizzy on its side, is the little drain hole in the right place?

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                • #9
                  Re: Oil in the distributor - 48D4

                  Hi Don. Yes my dizzy does have a drain hole about half way along the casing that is within the cam cover. I have it facing down. I assume this is correct.

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                  • #10
                    Re: Oil in the distributor - 48D4

                    Just for completeness I have checked the compression across all cylinders, both dry and wet and they are well within spec for a used engine. Add that to the knowledge that the breathing seems ok I'm left with the conclusion that I have a duff distributor - albeit a brand new one. I've contacted the supplier, A Series Spares, to get their take on my findings. For info, I've spoken to The Distributor Doctor and he can rebuild my old distributor for £175 plus Vat; not cheap as was mentioned in an earlier post but may be the way I'll have to go. Many thanks again for all the advice you've given.

                    Cheers Alan

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