B20 PCV questions
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    1. #1
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      B20 PCV questions

      I'm working with @clevolvo on a 142s with a B20 and would like some input (or even some definitive answers).



      From this Swedish Embassy page, it appears
      A) that the hose leaving the Oil Trap should go into the Intake Manifold (and it appears that the (red) hose on this engine once did), and
      B) that the hose going into the Oil-Filler Cap should come from the Air Filter.

      When received from the PO, these two hoses were loose under the hood. When connected the way described (Oil Trap to Intake Manifold and Oil-Filler Cap to Air Filter), the engine won't run.

      Questions:
      1) Is this configuration correct? (If not, what should it be?)
      2) Is a PCV valve on the Oil Trap needed? (currently only a flame guard there)
      3) Should a PCV valve also be on the air filter end of the oil-filler cap hose?

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    3. #2
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      I believe the B18 used that configuration and the B20 used the reverse (flame trap to filter, oil cap to intake). Either way works. One thing, though, the fitting that you use to attach either hose to the intake needs to have a reducer inside. You don't want full intake vacuum on your PVC system. How do your brakes feel? Maybe check the fitting that your booster attaches to for that reducer.

    4. #3
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      B18 & 20s have had flow in both directions which changed with the vintage and fuel injection versus carburettor arrangements.

      PCV.JPG

      On my B20E, the oil separator (#4 or #5) is connected to the air filter housing. Fumes exit the oil filler cap and are connected to a restricting nipple on the intake manifold. This works well on a Djet. On a carb equipped car the carburettor has to be set up to deal with the unmetered air entering the manifold. You have a non OEM carb, so you get to wing it!
      Last edited by 142 Guy; 07-16-2019 at 03:05 PM.
      A 142 of course. What do you expect? I'm the 142 guy. / 1971 142 E 102 color

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    6. #4
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      Regardless of the direction of the air flow, the connection to the intake manifold requires some sort of restriction. Otherwise way to much unmetered air flows through the PCV system. You will need a restricting nipple of some kind to put in that port where you show the red hose going to. Even then, if the carb is not set up to deal with this, you will have problems.
      A 142 of course. What do you expect? I'm the 142 guy. / 1971 142 E 102 color

    7. #5
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      fust...;

      As noted on that page, and others point out...flow direction (B18 or 20 configuration) is not important, but flow restriction is...in your case, I'd connect Oil Filler Cap to Air Filter (fresh air source), and replace plug in Intake Manifold with a hosebarb, and connect Crankcase there (assure there is a flow restriction in this extraction path).

      Cheers

    8. #6
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      On the normal B20 X, the restriction is in part #15 or #48 which screws into the stock intake manifold. This part also does double duty as the barb for the hose. You need to score the appropriate part:

      947043 - B18A / B18B

      http://212.247.61.152/us/main.aspx?p...e&artno=947043

      460082 - B20 A / B / E / F

      http://212.247.61.152/us/main.aspx?p...e&artno=460082

      The 460082 B20 nipple has a very small hole in it (this is what I have on my B20E). I don't know what the 947043 nipple is like. Don't try to use a conventional brass barbed fitting for this job. Any barbed fitting that will fit that red hose will have way too much air flow through it unless you fabricate a separate restriction in the suction path.
      A 142 of course. What do you expect? I'm the 142 guy. / 1971 142 E 102 color

    9. #7
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      Thank you all! This give me some things to work on this weekend. I'm looking forward to it.
      When we get this resolved, I'll report back.

    10. #8
      Junior Member mathue's Avatar
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      Quote Originally Posted by fustilarsic View Post
      I'm working with @clevolvo on a 142s with a B20 and would like some input (or even some definitive answers).
      Hehe, this subject seems to come up every once and a while.

      On my first 1970, the 145S, the filler cap (with some very rudimentary separating 'media' internally) went to a nipple with manifold vacuum behind it, the nipple had an orifice that was about 1/16". The connection for the oil separator went to a connection on the stock air filter housing.

      The loop was filtered air > side of the engine > through and up > then out through the cap and into the intake to have the oil vapour burned.

      Oddly this was reversed on some engines. I don't think it's too terribly important which way the fresh air enters and later the vapours get pulled out, just so long as IT GETS DONE. The oil lasts longer getting rid of contaminants.


      An interesting tidbit from when I went through some engine training many years ago is that the vapours, whether fuel or water tend to collect at the top of the engine due to heat. So at least in theory removing them from the topmost of the engine should be most effective.


      This is how my current 1970 142S is set up. I don't have a nipple with an orifice on manifold vacuum, however, I just use a generic PVC valve.

      Tomato, Tomatah.

    11. #9
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      Thank you all for the advice. We ended up going from Oil Trap to Intake Manifold through a new 2mm reducer. And the Oil-Filler Cap went into the Air Filter.
      And everything worked. Thank you.

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