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Projects Flathead valve lapping

Discussion in 'Traditional Hot Rods' started by diiulio, Nov 30, 2013.

  1. diiulio
    Joined: Dec 1, 2006
    Posts: 47

    diiulio
    Member

    I started lapping my valves and as usual, I have a question. How much of an area should have the grind mark on it for the valve seat? The exhaust seats are hardened, but the intakes are not. The machine shop ground the valves when they machined the block. I have new SS valves, stock intake 30 degree and exhaust 45 degree, I gave the shop the valves so they knew what I had. I lapped one side of the engine, intake and exhaust and they all seem to have the same small ring on the valve seat. How much is typical for having grinding marks on it? Also, one of the valves seems to have a little gouge in it that may or may not leak, how do I check this?

    This is what the seat looks like after lapping
    [​IMG]

    That is about .111" ring on the seat, about half the area after lapping
    [​IMG]

    Ring on the valve from lapping
    [​IMG]

    Unlapped vs. lapped valve
    [​IMG]
     
  2. Heo2
    Joined: Aug 9, 2011
    Posts: 661

    Heo2
    Member

    0.111 Contact area sounds fine to me
    cant see it in the pickture but do you
    got "lapping" marks 360 degres around the seat
    Then its fine
    Though for high perf use i hade made the
    seat bigger as in farther out on the valve
    not wider Contact area
     
  3. ronnieroadster
    Joined: Sep 9, 2004
    Posts: 708

    ronnieroadster
    Member

    It looks like to me the valve angle is not the same angle as the valve seat. The photo of the valve shows a very thin line this line should be much wider after lapping. Seeing just a fine line would indicate there's a big difference between the two surfaces.
     
  4. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,306

    henryj1951
    Member
    from USA



    A lot of that could be a 44* valve on a 45* seat.


    :cool:
     
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  5. Russco
    Joined: Nov 27, 2005
    Posts: 4,065

    Russco
    Member
    from Central IL

    Mine was quite a bit wider than that and I thought it should have been more.
     

    Attached Files:

  6. ottoman
    Joined: May 4, 2008
    Posts: 272

    ottoman
    Member
    from Wisconsin

    U check with a vacuum setup.... drop valve in with no spring and put the vacuum guage/pump over port... I ran a Serdi for many years and the Vac checker was part of the machine used to final check the VJ. cant find a pic right now.
    Yea seat looks a little low to me
     
  7. George Miller
    Joined: Dec 26, 2008
    Posts: 413

    George Miller
    Member
    from NC usa

    A wide seat is not a good seat. You will burn the valves quicker with a wide seat. It will not seal as well, and does not transfer the heat as well.
     
  8. R Pope
    Joined: Jan 23, 2006
    Posts: 3,310

    R Pope
    Member

    My Ford shop manual says 45 deg seats both intake and exhaust, minimum 1/16" wide.
     
  9. PushnFords
    Joined: Dec 2, 2011
    Posts: 52

    PushnFords
    Member

    If you don't have a way to vacuum check the valve seal I've used gas. If it holds gas then it should be fine...can check rings like that too on an assembled engine. It'll leak through the rings but rate can pinpoint a problem.
     
  10. aonemarine
    Joined: Nov 2, 2013
    Posts: 501

    aonemarine
    Member
    from Delaware

    kinda looks like the exhaust is 30 and intake 45 on the seats?
     
  11. old gezzer
    Joined: Oct 25, 2012
    Posts: 23

    old gezzer
    Member

    It is unnecessary to lap valves when the valves and seats are properly ground with precision machinery. When a interference angle is used 44 valves and 45 seats the interference angle will provide a line contact the valve will seal very well. The interference angle also provides a way for the valve/seat to force carbon out.
    Another thing to consider is that the valves and seats expand a different amount so the lapped areas of the valve and seat will not match when the engine is running.
    Marv. W.
     
  12. aonemarine
    Joined: Nov 2, 2013
    Posts: 501

    aonemarine
    Member
    from Delaware

    Yes but typically when you lap a valve that has an 1deg interfearance fit it will quickly lap down and show a pattern for the full seat width. that thin band of a lap just does not look right to me.
     
  13. wood470
    Joined: May 21, 2008
    Posts: 225

    wood470
    Member

    I was always taught to go for the thinest ring that went all the way around. A multi angle grind which is even better will provide a very small contact ring.
     
  14. HotRodMicky
    Joined: Oct 14, 2001
    Posts: 1,756

    HotRodMicky
    Member

    A flathead has 45 degrees on intake and exhaust !
    So you must have matching valves.
    No 30 degrees
     
  15. Heo2
    Joined: Aug 9, 2011
    Posts: 661

    Heo2
    Member

    Thats true. I use the lapping only to check thats
    the seat is true to the valve if you get lapping
    marks around the whole seat its fine
    Problem with a flathead is the headbolts
    distort the seat so to get it 100% you need
    to have a stressplate bolted down when you
    grind the seat if whe want to bee anal about it.
    wide seats is bad for sealing bad for flow
    1.5 -2 mm is enough
     
  16. diiulio
    Joined: Dec 1, 2006
    Posts: 47

    diiulio
    Member

    I am not sure, aren't the intake valves 30 degrees? This is what I have...

    Let me know if I have the wrong intake valves.

    [​IMG]

    [​IMG]
     
  17. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    I have intake 1.2-1.5 mm ,exhaust 1.5-1.7 mm
    Exhaust for better cooling through the block slightly larger
     
  18. I always lapped with bluing liquid at this point. Makes for a better visual.
     
  19. seb fontana
    Joined: Sep 1, 2005
    Posts: 5,864

    seb fontana
    Member
    from ct

    My first thought also..Lapping should end up as pic in post #5..Maybe the valves are packaged wrong, the op pics to me with the "ring" so far down the valve indicate 44/45° valve and 30° seat...
     
  20. aonemarine
    Joined: Nov 2, 2013
    Posts: 501

    aonemarine
    Member
    from Delaware

    Look at the very first picture in the thread.....:confused:
     
  21. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    I have used 45 ° for valve area, valve head 90 ° in the upper area, 75 ° in the valve base to cut free.
    the 90 ° and 75 ° were milling cutter on a guide, 45 ° is fine grindstone on leadership.lapping was then almost unnecessary.

    I hope my bad english is understandable:confused:
     
  22. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    [​IMG]

    a) valve perfect

    b) valve to high

    c) valve to deep
     
  23. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    [​IMG]
    valve seat correction
     
  24. diiulio
    Joined: Dec 1, 2006
    Posts: 47

    diiulio
    Member

    The question is, am I good to continue? I want to make sure these valves and seats are good before I continue with the build.

    Thanks for all of the input. Based on the recommendations I have dyed the valves and seats using a sharpie marker. I have only done the driver side cylinders so far, they are number 5, 6, 7, and 8 from front to back, respectively. I have labeled the block for 5I and 5 E, for intake vs. exhaust. It seems that the intake seats sit near the edge of the valve and the exhaust sits toward the inside more.

    Most are around .100", and one of the narrow ones is .060". Based on your comments I think I am ok to continue. I did notice a little tiny gouge on the 6 intake near the 6exhaust, I am not sure if that is something I can just lap a little more to clean up.

    Cylinder 5
    [​IMG]

    Cylinder 6
    [​IMG]

    Cylinder 7
    [​IMG]

    Cylinder 8
    [​IMG]
     
  25. aonemarine
    Joined: Nov 2, 2013
    Posts: 501

    aonemarine
    Member
    from Delaware

    I don't like where the exhaust valve is seating....
     
  26. knucklepower
    Joined: Jan 9, 2009
    Posts: 148

    knucklepower
    Member
    from .

    Valve area grinding is your first job. Lapping is step two. Look at my Pics.


    Posted using the Full Custom H.A.M.B. App!
     
  27. Jimmy2car
    Joined: Nov 26, 2003
    Posts: 1,707

    Jimmy2car
    Member
    from No. Cal

    I agree with Aonemarine. Seat should be much more centered
     
  28. john walker
    Joined: Sep 11, 2008
    Posts: 1,068

    john walker
    Member

    exhaust seat contact area needs to be moved outward, so the contact area looks like the intake valve. either that or you have the wrong valves. (too big?). 1.5 to 2mm width needed to help conduct heat from the valve to the block.
     
  29. Mr48chev
    Joined: Dec 28, 2007
    Posts: 25,415

    Mr48chev
    ALLIANCE MEMBER

    Yep, that is the standard procedure when grinding valves and has been for the 50 + years I have been working on cars.

    The guys are right in that it does appear that the seats haven't been done to properly get the contact area on the seat so that it hits the face of the valve in the right spot. It looks like they installed the seats, gave them a clean up touch to get good contact with the valves but didn't take the time and effort to properly dress them so that they contacted the valves in the desired spot. The thinking was probably that they were leaving the seats so that they could be ground again with plenty of meat left for the second and maybe third redo.
     
    Last edited: Dec 2, 2013
  30. tig master
    Joined: Apr 9, 2009
    Posts: 416

    tig master
    Member
    from up north

    You say stock 30 deg int no way that is stock they are 45 deg. Did the mach shop know you switched to 30 deg intakes. If they were unaware your seats will be 45 deg and did they have the valves to look at?

    T
     
    Last edited: Dec 3, 2013

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