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is the oil filler / breather 289 full flow in the center better than being on the valve covers?

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  • Engine: is the oil filler / breather 289 full flow in the center better than being on the valve covers?

    can a single breather on the valve cover provide enough air supply for the PCV? then why do I see 2 breathers on some engines?

    does having the breather on the valve covers direct the air flow from the top of the head, thru the push rod holes, the oil galleys or both?

    or does it function identically and the center oil filler breather reaches into the crankcase?

    from an esthetic aspect i think the breather on the cover look a bit more tidy, , what is involved to eliminate the center filler tube?

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  • #2
    All good questions.
    The PCV systems were just being introduced at the tail end of Studebaker engine manufacturing.
    Several aftermarket companies introduced 'kits' to put PCV valves on engines.
    At the time PCV's first came out they were an open type system that just pulled some fumes out of the crankcase rather than seeing them dumped (siphoned) out the road draft tube. Later systems sealed the PCV loop completely.
    So, the give you answers (or spur further conversation) to your questions:
    On a stock engine, the one breather was adequate to keep the crankcase pressures neutral. The road draft tube would siphon out crankcase fumes and fresh air was drawn in through the oil filler cap screen.
    All you are doing by adding a PCV valve in place of a road draft tube is re-routing the crankcase fumes into the intake manifold to be burned again, reducing polluted fumes.
    As far as placement of the breathers? Other accessories made the real estate at the front of the engine more valuable to the OE component placement people. You can count on the OE to not do anything they did not have to do that added cost to production.
    I have never seen a production Studebaker that had a completely closed PCV system. Maybe someone more knowledgeable can chime in there...

    HTIH (Hope The Info Helps)


    Get your facts first, and then you can distort them as much as you please. Mark Twain

    Note: SDC# 070190 (and earlier...)


    • #3
      The center fill was there because in the old days when your motor was burning oil like a furnace it was easier to pour oil in from a Gallon jug of recycled 40 weight. (When you drop in an R4 to keep up with the LA traffic you’ll enjoy 4 breather caps)


      • #4
        i have seen hoses connect to the clean air side if air filters , the aftermarket chrome also has a nipple ( large) that is capped off, i believe some breather caps instead of a screen, limited it's supply air stream to a port ( idk how well it seals and leak unfiltered air around the filler tube.

        in my case the1406 edelbrock carb front center port, is connect to a PCV of unknown application or orgin , via rubber and bent aluminum tubing that (PCV)is located on the rear on the Valley cover.
        Uunsure what OE if any equipment was eliminated to accommodate this modification, or was it's Stude version of PCV routing,

        other car's PCV port would utilize the opposite valve cover, making for a more throughout evacuation , or maybe it doesn't matter; ot maybe any vacume would be able to suck all the gases all the time.

        the valve covers i have seen with breathers have 2 hold down studs my car has 4, i like the four, no big deal, it is easier to add oil since the filler is straight up
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        • #5
          mw -

          A good running engine can live on the road draft tube (valley cover) and the center location, block breather just fine. A worn engine needs all the air openings it can get !
          The rocker cover breathers help a little, but as you state, the only breathing that's done at the small, leftover difference between the pushrod holes vs the pushrod diameter.
          Then to add to that, is the Avanti's, oil pan breather ! That one is the best of the bunch, because that's where the blowby starts.

          To instal a PVC system, you need to plug all other openings. One breather opening goes to the PCV valve and to the carburetors, "full" vacuum port.
          One other opening (to be govt. legal), needs to go to the air filter housing, to breath "cleaned" air.
          Where either of these locations come from doesn't matter, but the better breathing locations, the better the system will be. The valley cover and the center block stand are the best places for both of the above.

          NOTE - The OEM chrome breather caps...don't do much if anything if at all. Turn them over, there is NO airflow path, the underside of the cap is solid. The only flow path is the leakage from the tube up through the caps inner diameter and into the rocker cover tube.
          Unlike a more "normal breather" caps, the airflow path is through the inner part of the cap, through some sort of filter medium, up through the center, and down through the caps center. Again, the Stude OEM cap does not have this path.



          • #6
            So a quick upgrade is put in a filler cap that can move more air? and would it not be better to not have grit potentially enter the engine with a non filtered cap?


            • #7
              Breather caps; now there's a subject I can get my teeth into!

              Attached is a pic of two breather caps off my 64 Avanti R2. Note that one has two small holes (1/8 in.) inside for air to pass through; The other has no holes. Both came off my 64 Avanti. So, I'm puzzled why one has the holes and the other does not. I've always seen these V8 breather caps with the two small holes (on 63-64 V8s).

              My other car, a 64 Hawk R1, has the two holes in both breather caps.

              By comparison, the second pic is of an R3 breather cap. It has a wide-open cap. No PCV system here!

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              Last edited by Dwight FitzSimons; 02-28-2021, 10:09 AM. Reason: Corrected diameter of holes


              • #8
                who knows who changed what on the cars, and perhaps there is a difference without a distinction, and doesn't amount to a few hundred miles of extra engine life, other factors may contribute more or less to that,

                but I should take a closer look and break out the drill to increase flow
                Last edited by mw2013; 02-28-2021, 10:57 AM.


                • #9
                  I revised my post above after measuring the holes (1/8 in.).


                  • #10
                    Originally posted by Dwight FitzSimons View Post
                    I revised my post above after measuring the holes (1/8 in.).
                    Interesting comparison you have. Clearly three different flow rates for the three caps, and for what reason I have no idea. I don't even know which ones are on my two GTs, but will look soon, just to know. I'd think the one with open top, for free flow, would be most logical, but I have never even looked as a cap that closely.


                    • #11
                      1) everyone else did it 2) it eliminated the stand pipe since it cost $ and no longer served a purpose - supporting oil filter. 3) and the standpipe was in the way with the R2 supercharger and those dumb rubber hoses could leak. I seriously doubt that one is better than the other, but I 'spose you could argue better ventilation especially under the rocker arm covers. More often than not changes were made not for improved performance and reliability but for convenience and cost. I imagine the 'flow rate' depends on how much dirt and congealed oil has accumulated over the decades, too. You would have to measure total surface area of all the holes and ,yes I am bored, but nowhere near THAT bored!


                      • #12
                        guess i don't have to drill, mine is full flow

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                        • #13
                          AFAIK, the caps that are completely open are for a non-PCV engine (62 & back except for California, which would be 60 & back). Those let the crankcase fumes flow out under the internal pressure in the engine crankcase. Those with the 1/8" holes (or no holes) meter a small amount of air IN on a PCV system. Crankcase fumes then will be drawn into the engine intake and burned. I wouldn't think that the little holes would matter much because the caps are a loose fit on the valve covers anyway.

                          Anyone wanting the open caps might look for 6-cyl caps (that's where I've found them). Those will be an even looser fit because they fit on a larger tube.


                          • #14
                            so it might be better to create low pressure environment in the crankcase, if i have a PCV and the wide open cap I have may not create enough vacuum?


                            • #15
                              The PCV system keeps the engine a lot cleaner internally. I'm not very familiar with the systems, so one would have to check the Stude parts catalogs to determine what parts are used on a particular engine.