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Thread: Max Valve Lift in V8

  1. 13th May 2011, 09:46 AM #1
    Phil257
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    Max Valve Lift in V8

    Hi Guys,

    Getting close to having my engine running. Its a 3.5 late 70's (not Stiff Block) with single valve springs. I'm running a Crow Cam 37776
    Specs are
    Valve Timing
    IN. 25/65
    EX.74/26
    Advertised Duration
    270
    280
    0.050" Duration
    204
    214
    L/C
    112
    Max Lift
    IN .420"
    EX .442"
    Rev Range
    1800
    4800
    Dual pattern cam for maximum driveability in
    street modified engine.

    I'm a bit concerned about the .442" lift causing coil bind with standard springs.
    Is anyone out there running this cam or similar lift with no valve train modifications

    Any helps appreciated,

    Cheers,

    Phil
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  2. 13th May 2011, 12:17 PM #2
    PhilipA
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    All I can do is refer you to "How to Power tune Rover V8 Engines" Chapter 6 Camshafts and Valve Springs page82
    heading "1976 -1993 Cylinder Heads"

    "The single valve springs of all engines fitted with such (1976-2004) will need to be changed to prevent coil binding if more than .430ins/10.9 MM of valve lift is to be used."
    The book quotes Piper VSSV8 which has one less coil so is OK.
    Regards Philip A
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  3. 13th May 2011, 01:14 PM #3
    Phil257
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    Thanks Philip,

    I've been looking into it a bit further, and have been told that while coil bind might be okay, the standard valves will likely break due to harmonic oscillations at higher lifts and should be replaced. Looks like a new set of springs is in order before I fire it up.

    Cheers,

    Phil
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  4. 13th May 2011, 06:16 PM #4
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    djam1
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    I once had a high lift cam put in a 3.5 foolishly I didnt change valve springs and it broke a valve spring within 2000km
    Be careful its annoying to have to remove all the broken bits
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  5. 1st June 2011, 12:35 PM #5
    Phil257
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    I've got my new valve springs now. Supposedly good for .6" lift and fitted with a damper spring. Hopefully get them fitted up this weekend. At least this way if I dont like my cam I can easily change and not have to worry about lift (not that I'll ever get anywhere near .5" let alone .6").
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  6. 1st June 2011, 11:39 PM #6
    33chinacars
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    Hi Phil Should have got a set of valve springs from Crow to match your cam. Watch out you dont have to much valve seat presure or you will end up with valve seat recession. Not an overly wild cam so shouldn't need to strong a spring but consult Crow for exact specs
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