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Technical valve seat width

Discussion in 'The Hokey Ass Message Board' started by seb fontana, Apr 1, 2020.

  1. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,532

    seb fontana
    Member
    from ct

    Wanting to do 30/45/60° seats with a 3 angle tool. Valves are small, 1.050 exh and 1.150 Int. So how wide should I make the seats? Spring pressure is about 60# on the seat, rpm 7500 +/- 1000. Valves will be back cut to lighten and for flow. How does .045 int and .060 exh sound?
     
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  2. Mr48chev
    Joined: Dec 28, 2007
    Posts: 27,204

    Mr48chev
    ALLIANCE MEMBER

    That is narrower than I used to do them. most of the ones I did were just over .100 but I am seeing anything from .065 .100 when I looked it up right now.
    I'm going to call it engine builder's personal preference and that things may have changed a lot in the past 25 years since I was doing valve jobs and teaching students to do them.
     
    Last edited: Apr 1, 2020
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  3. DOCTOR SATAN
    Joined: Mar 21, 2014
    Posts: 711

    DOCTOR SATAN
    Member
    from okc

    'bout 2/3 the way out is how we do them on old Harley floater motors....
     
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  4. KJSR
    Joined: Mar 7, 2008
    Posts: 2,276

    KJSR
    ALLIANCE MEMBER
    from Utah
    1. Utah HAMBers

    I typically cut to about .060 max and had good success
     
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  5. onetrickpony
    Joined: Sep 21, 2010
    Posts: 437

    onetrickpony
    Member
    from Texas

    My experience has been that the narrower the seat, the better the short term seal but the shorter the life of the valve job. My usual compromise was .060 and .090 for acceptable life and good performance.
     
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  6. gary terhaar
    Joined: Jul 23, 2007
    Posts: 655

    gary terhaar
    Member
    from oakdale ny

    .045 and .060is just fine,most of my street and hot street work is in that range.
    No one mentioned valve guides.
    If the guide is straight and true,it helps longevity 10 fold,heat transfer from the valve is better. A quality valve and correctly sized guide is a must.
    A new guide or service liner,then honed to size not reemed.
    The valve job starts at the guide.
    In time the seat with gets wider with use,so do worry about it. As long as your guides are good and seat concintricity is good your service life will exceed original oe.
     
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  7. saltflats
    Joined: Aug 14, 2007
    Posts: 10,198

    saltflats
    Member
    from Missouri

    Doesn't the valve determine the width of the seat?
     
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  8. They are referring to the contact area between the valve and the seat in the head


    Sent from my iPhone using H.A.M.B.
     
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  9. saltflats
    Joined: Aug 14, 2007
    Posts: 10,198

    saltflats
    Member
    from Missouri

    I understand that, I make my seat width narrower than the width of the valve
     
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  10. Mike VV
    Joined: Sep 28, 2010
    Posts: 1,980

    Mike VV
    Member
    from SoCal

    If this were my cylinder head -

    Intake = .060"
    Exhaust = .090"

    Normally wider will result in a loss of quality flow.

    Mike
     
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  11. @seb fontana generally speaking wide seats on a huffed mill and narrower on a naturally aspirated motor.

    On a small valve I would be shooting for .06 to .12 probably closer to the .06 side. I have a tendency to run a wider seat on an air cooled motor than I do on a liquid cooled motor. But it is a personal thing I think and I cannot give you any good logic on it.
     
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  12. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,532

    seb fontana
    Member
    from ct

    Valve guides are good at .312, I have a choice of .310 or .315 stems so any clearence can be made. Beaner brought up what I forgot; eventually I do plan to get to a few pounds of boost.. I left the compression at 8:1.. My thought beyond performance gains of narrow seats is the ability for the valve to "bite through/Crush" any trash, carbon, etc. Stock seats were in the .075/.090 range, valves have just over .100 face. I put my dail calipers at .045 and .060 and I get nervous, sure isn't much!
     
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  13. I always shot for 1/16 ".
     
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  14. THE FRENCHTOWN FLYER
    Joined: Jun 6, 2007
    Posts: 3,081

    THE FRENCHTOWN FLYER
    Member
    from FRENCHTOWN

    X2 what gary says. I love the job my Sunnen valve guide hone does.
    What is the intended use of the engine? You mentioned a 7500 RPM intended operating range. Is it for a street application or a race application. Race cars can get by with narrower seats further out near the outer edge of the valve face. Never at the extreme edge of the valve. For street applications I go a little wider. Longevity trumps optimal flow here.
     
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  15. gary terhaar
    Joined: Jul 23, 2007
    Posts: 655

    gary terhaar
    Member
    from oakdale ny

    On the intakes I run .0014-.0015 ,exhausts .0017-.0018 except for the two siameed exhaust ports I run them at .0020 .
    A proper bore gauge ,split type I use,or a sunnen is needed,without a bore gauge you are just guessing . Pin gauge,go/no go or a ball style snap gauge like mondello use to use in his classes,cannot show how straight it really is. Using the right measuring tools is a game changer. I use to reem with carbide reems, measured them with a bore gauge and never picked them up again.
    When the guide is straight to the .0001 the valve doesn't thrust,hits the seat true and consistant and durability and longevity is increased.
     
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  16. ekimneirbo
    Joined: Apr 29, 2017
    Posts: 1,284

    ekimneirbo
    Member
    from Brooks Ky

    Why do you feel a carbide reamer won't ream a guide properly ? Can you explain how you check straightness? Do you use a precision air guage for verifying the inside of the guides?
     
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  17. gary terhaar
    Joined: Jul 23, 2007
    Posts: 655

    gary terhaar
    Member
    from oakdale ny

    I use a mitatoyo split bore guage it will read the bore of the guide as you pass through it,a air guage is fixed to a table or stand,really can't hold the head to use one.A fixed guage just reads the tightest point. Every guide I measured done with a reemer always shows tight in the middle,less deflection on guide supported better in the middle. And they generate a wavy pattern seen on the guage while passing through it. Honing the guide gives a perfect finish and you can dwell while honing the guide to ensure straitness. If I end up .0002 taper or off my size. it's alot for me.
    You will get a thousand people tell you it's overkill, what works and what works well are two different things.
    You won't find a auto parts machine shop doing this type of work.go to a real speed shop, someone with a reputation of good work ask what they do. I am not far off and yes,this is what I do.
     
  18. DOCTOR SATAN
    Joined: Mar 21, 2014
    Posts: 711

    DOCTOR SATAN
    Member
    from okc

    Unless your machinist also builds race mills.....that's a plug for Paul at balsinger machine, Guthrie, USA.....third generation machinist, and a great guy...honest to boot
     
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  19. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,532

    seb fontana
    Member
    from ct

    Well I got tired of trying to port the valve bowls around the guides so I knocked them out (pressed). I can get new guides in cast iron or bronze. Is one really better than the other for the size of the valves [1.150&1.050-.310 stem]? Rpm at 7500 is conservative, being a Crosley, over that and the trans becomes issue. I figure I can lean on the tight side for stem clearance as there should be no side load from rocker arms as it is sohc; cam, lifters, valves. Or am I thinking backwards? I got a seat cutter that can swing doing both valve diameters and seat widths [just barely], arbor too.
     
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  20. Pete1
    Joined: Aug 23, 2004
    Posts: 1,787

    Pete1
    Member
    from Wa.

    Bronze guides will transfer heat better.
    A radius valve job will gain you about 3% hp.
     
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  21. seb fontana
    Joined: Sep 1, 2005
    Posts: 6,532

    seb fontana
    Member
    from ct

    Up date. Stalled for three months, hand issue with Rheumatoid arthritis. They swelled up so much I couldn't bend my fingers [hurt], got meds and heading back to usable. Got a eurolift too, made things a little better but ways to go..My hands have lost a lot of callas except for my right hand;o_O no not from that. From running the computer mouse..
     
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