Valve Rotation

Discussion in 'Volkswagen' started by gammaxy, Jan 9, 2018.

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  1. Jan 10, 2018 #21

    Pops

    Pops

    Pops

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    I wouldn't use a VW head without the baffles that Bob Hoover is talking about in the link. About Revmaster heads-- Think I read somewhere that there is more fin area. Revmaster is the oldest VW aircraft conversion company in the business, I believe they started in 1968. To many people put VW engines in airframes that require the engine to be run to hard for the design.
     
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  2. Jan 10, 2018 #22

    Daleandee

    Daleandee

    Daleandee

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    The Remaster heads may be better but IMHO a great head for a VW aircraft conversion needs a single port and more room between the valves. Smaller valves could help prevent head cracking between the valves. The big valve, dual port heads, are designed for the race engine guys but the airplane conversions don't need heads that will breathe at 7000 RPMs. I'd even entertain the thought of single plug heads with a hot enough ignition source so a wider plug gap could be used with better plug technology (iridium?).

    I should clarify that it's not my intent to be negative at all about the Sonex. As originally designed it was to be an airplane of about 600 lbs empty weight (Jabiru 2200) and would be a fun flyer for around the patch and the occasional hamburger run or fly-in. Things have changed and the design now has a nose wheel (more drag) and a lot more weight being added by builders that want to fill it with creature comforts and fly it cross country. The VW was/is an entry level engine to allow a builder to fly a fun airplane for little money (relatively speaking). But now they seem to be closer to 700 lbs empty with builders bumping up the gross weight so as to have a a reasonable useful load capability. Now the little engine that could, still can, but it just has to have more care to help it keep up. As I noted earlier, if a builder doesn't mind chasing the head/valve issues when working the engine that hard, the VW in a Sonex will work for them. I had a VW Sonex and I absolutely loved the way the air frame handled and it was that airplane that brought me to the one I have now. I wanted a Jabiru 3300 engine on a tail wheel after I flew one because that much horsepower made the airplane come alive! I ended up with the Corvair for various reasons and I'm glad I did after seeing some of the heartburn that others have had with the Jabiru engines.

    A pilot flying in the 35 hours a year range (latest average?) could likely get three years on a good set of VW heads. All things considered that's not bad at all when you look at the cost of some of the other options. The money my friend spent on three annuals on a Cherokee 140 would have nearly replaced my engine.

    Dale Williams
    N319WF @ 6J2
    Myunn - "daughter of Cleanex"
    120 HP - 3.0 Corvair
    Tail Wheel - Center Stick
    Signature Finish 2200 Paint Job
    166.7 hours / Status - Flying
    Member # 109 - Florida Sonex Association
     
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  3. Jan 11, 2018 #23

    Pops

    Pops

    Pops

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    Very good post. The VW dual port head starts to breath better at 3000-3200 rpm and above. In a straight drive VW engine the single port head will turn the prop better below that RPM than the dual port engine and there is no problem with cracks between the spark plug hole and the valve seat. With single port heads I use 1 1/4" dia intakes instead of the 1 1/2 dia used on dual ports heads. Gives a higher intake velocity that packs more air in the cylinders. The difference is amazing.
    New single port heads ---- http://www.jbugs.com/product/311101353AC.html
    http://carcraftstore.com/brandnewsingleportcylinderheads.aspx
    http://www.mamotorworks.com/VW/subcategory/engine-cylinder-heads-single-port
     
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  4. Jan 11, 2018 #24

    Marc W

    Marc W

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    Would single port heads breathe well enough for a 2180 cc VW up to about 3000 RPM? If so I might try a set. I am not really interested in spinning the engine over 3000 RPM.
     
  5. Jan 11, 2018 #25

    Pops

    Pops

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    I need to finish my flywheel drive , single port heads drilled for dual ignition, 2180 cc engine with a Zenith carb. I want a mag on the pulley end and no one sells one, so making my own.
     
  6. Feb 4, 2018 #26

    samyguy

    samyguy

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    Hi guys; Take look at both a single port and duel port heads exhaust cooling fins.
    You will see that the single port has passages or holes for cooling air to flow though.
    Now look at the Duel port head, those same passages are closed off with casting flashing
    or when the head was cast, the mold was worn and the holes were not left open.

    Gammaxy quoted BOB HOOVER go read all of what he has written, good stuff.

    Now those passages or holes need to be drilled and filed open to get proper cooling.
    Add a oil filler and a big oil cooler to up the oil capacity, this will help cool also.

    http://bobhooversblog.blogspot.com/2009/01/head-drawings.html

    http://www.eaa691.net/images/pdf/VW aircraft engine building.pdf

    Check out the head drawings closely, you will see what I'm talking about.
    Most of that can be done in the airframe.
    Then just as importantly get the high baffle kit from Sonic,and seal it well to your cowling.
    Get good air pressure though the motor cooling fins/passages to cool it.

    All credit goes to BOB HOOVER
     
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  7. Feb 4, 2018 #27

    Pops

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    Very good post. If you are interested in using a VW engine, you should read all of Bob Hoover's blogs. Its an education in VW engines.

    Local friend of mine did the fat fin mod on his VW engine that he was using in a Zenith 701 with a redrive belt. It did help the CHT a certain amount. He was running the engine very hard cruising at 3800-3900 rpm and on the way to OSH the case cracked at 78 hrs if I remember correctly. Just trying to get to much HP from the engine for the design. He replaced it with a R-912 engine.
     
  8. Feb 4, 2018 #28

    Marc Bourget

    Marc Bourget

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    In an earlier post in this thread, Pops said: "Most VW engine problems is a result running the engine with high CHT's for different reasons."

    I learned engine cooling from John Thorp. I have a 3" ring binder full of NACA reports and my "book reviews" of those reports. Most everything I learned validates Pops' point.

    I've attended many cooling seminars at OSH and avidly follow the RV forum threads (ref Dan Horton and RV6guy). Until I do some of my own testing, I'm not sure if anybody today has a full grasp of what the guys in the 40's and 50's understood about cooling piston engines.

    I have a question for TFF - on his post where he said: " . . but it will also wear the valve and seat out as it grinds it self down. "

    What with valve lash, I think the valve rotates between the keeper and retainer, not valve and keeper. Additionally, I also think the mechanism of rotation is while the rocker is in contact with the valve head, not while it's on the seat. But that's just "my think" if I'm wrong, please let me know.
     
    Last edited: Feb 4, 2018
  9. Feb 5, 2018 #29

    BBerson

    BBerson

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    The valve rotation for the VW is explained in the second link of post 26.
     
  10. Feb 5, 2018 #30

    pictsidhe

    pictsidhe

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    I've watched a few engines idle with the cover off. The springs caps have rotated on all of them.
     

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