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Thread: Excessive Blowby?

  1. #1
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    Excessive Blowby?

    Hey All

    I have a 1950 Buick. The engine runs well and moves down the road fine, but to my eyes, the blowby seems excessive. It seems to more prevelent when first started and driving, but there is really not too much difference cold or hot. Of course, prior to the PCV era, some amount of blow by was obvious and normal. This to me seems to be too much. I doubt there is an easy fix, but short of a rebuild, is there anything I can do to minimize the smoke? Thanks in advance for any thoughts or advice you may have.

    Mike

  2. #2
    Install a PCV valve
    Tom Telesco
    Classic and Muscle Automotive
    12 Cook St.
    Norwalk, CT 06853-1601
    Day Phone 203-324-6045 ET
    NailHead Mini-Starters '53-'66
    Adjustable Roller Tip Rocker Arms - All NailHeads
    Custom forged pistons
    Front & rear neoprene seals
    Many other "Nail" parts
    "If I can't get it, you don't need it!"

  3. #3
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    Quote Originally Posted by telriv View Post
    Install a PCV valve
    telriv

    Is this something that has been done before by you or others? I wondered about that, but dismissed it because I thought there were other details that had to be considered. Thanks for the response!

    Mike

  4. #4
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    Quote Originally Posted by Mike1947 View Post
    Is this something that has been done before by you or others?
    Mike
    A fair number of cars were converted to PCV in the 1960s. At one time aftermarket kits were sold for doing this, but a kit isn't really necessary as the amount of fab work required is minimal.

    Ray
    Last edited by raycow; 06-24-2012 at 11:44 PM.

  5. #5
    Look at the way PCV valves are installed in '60's cars. Very easy to do with minimal fab work. Vacuum source needs to be a high volume area on the intake manifold & can be plumbed into the road draft tube. The hardest part will be drilling of the intake manifold & finding a grommet to fit the hole in the road draft tube. Don;t forget to block the bottom of the road draft tube. A PCV filter from a '70's car that would go into the air filter housing would be easiest.

    Tom T.
    Tom Telesco
    Classic and Muscle Automotive
    12 Cook St.
    Norwalk, CT 06853-1601
    Day Phone 203-324-6045 ET
    NailHead Mini-Starters '53-'66
    Adjustable Roller Tip Rocker Arms - All NailHeads
    Custom forged pistons
    Front & rear neoprene seals
    Many other "Nail" parts
    "If I can't get it, you don't need it!"

  6. #6
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    Ray and Tom

    Thank you for the responses, I do really appreciate them. So this was actually done in the past! Kind of surprises me now everything on the car is stock or original. The oil filler cap does not have what I understand as a road tube -- A rubber hose attached to the the oil filler cap or more likely a separate oil breather cap that would have that. I understand that the vacuum would have to be past the carb to keep the oil from causing problems for the carb base. Would I need to cut another hole in the valve cover to put the grommet and the PCV vale in place? I driven many cars with and without PCV vales, but have never done or even considered a retrofit. Again, thanks for the help, guys!

    Mike

  7. #7
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    A properly done and functional PCV system will pull a vacuum at idle. That means that you need to block the road draft tube, and use a non vented filler cap, and block the crankcase vent on the block side, and put an o-ring type seal on the dipstick. Then the PCV valve can be installed on an area like where the little vent on the block is or in the valve cover, or where the road draft tube connects. The other end of the PCV needs to be in a high vacuum area below the carb somewhere. An added benefit to a PCV system on an old engine is that it tends to pull a vacuum on the crankcase and pull oil into the engine at the crank seals and all other gasketed areas. [read, no oil leaks]. If the engine has lots of blowby, however, the crankcase will build pressure instead of vacuum at road speeds and push oil out of these areas. Yes, properly done the system will work, if the engine isn't too worn out. Hope this helps explain the function and operation of the PCV system.
    Doug

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    Sorry, A P.S. to my last post. Totally closing the crankcase is only for testing to see if you have any vacuum leaks in the system. You do have to have a filtered inlet such as a cap that is also a filter for the air to enter the system. The filtered inlet does have to be of sufficient size to allow a zero crankcase pressure/vacuum. Don't know what I was thinking on my earlier post.
    Doug

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    Doug

    Thanks for the response and information. If I understand the process, what I have now is a single breather on the valve cover that is open to the air with an internal fiber filter. I would need to:

    1 drill and tap for a hose barb in the intake below the carb base.
    2 modify the oil filter tube to accept a grommet and PCV valve OR drill the valve cover in some other location for the grommet and PCV valve OR locate the road draft tube and modify that to accept the PCV valve
    3 close off the road draft tube if not being used as the PCV valve location

    If my thinking is faulty, please let me know. I am OK mechanically, but this is the first Buick and first old technology that I have worked on personally. I need to locate the road draft tube -- I have an original shop manual to help.

    Again, Doug, thank you for your time and comments -- much appreciated.

    Mike

  10. #10
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    The road draft tube is attached to the pushrod cover on the right side of the engine, slightly forward of the engine mount.

    Ray

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