Gt40p Spring Rate With Flat Tappet Cam

Discussion in 'Fox 5.0 Mustang Tech' started by DTARS, Sep 1, 2013.


  1. DTARS

    DTARS Member

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    im sure this has been asked on this forum already, but i cant find a post on it.

    im not sure what springs/spring rates to use on my gt40p heads with a hydraulic flat tappet cam.

    im also using 1.6 roller rockers. any help info would be great thanks.
     
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  2. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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  3. DTARS

    DTARS Member

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    i havnt picked a cam out yet, was thinking about goin with a lunati or comp cams xe256, waiting till tues to give lunati a call
     
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  4. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    That's not an overly aggressive grind and flat tappet camshafts don't generally require as much spring as roller. Grab a set of these, they should do you fine and won't break the bank....

    http://www.alexsparts.com/sb-ford-g...ing-kit-hyd-roller-10-degree-retainers-locks/

    Heres a good read to provide you with a general perspective on the subject...

    http://www.kennedysdynotune.com/Valve Spring Tech.htm

     
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    Last edited: Sep 2, 2013
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  5. ID89GT

    ID89GT Active Member

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    Those are quite a bit cheaper than the Trick Flow ones.. has anyone ran them yet? I don't want to cheap out on something like that so just wondering what experiences people have had.
     
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  6. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    Many have used Dave's spring kits with great success. My buddy runs them in his roller 5.0l with more cam than you plan on running and he has zero issues.
     
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  7. ID89GT

    ID89GT Active Member

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    Hmm good to know. Us tight budget people enjoy finds like these :) lol. Ill just be using a TFS1 cam so nothing drastic.
     
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  8. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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  9. DTARS

    DTARS Member

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    ya so i ended up goin with a lunati voodo cam with the 351 firing order .
    i forget what duration tho.
    i ended up ordering the springs from alexes . but i accidentaly ordered 7/16 roller rockers instead of 5/16 , so im just gona drill n retap to 7/16ths , looks like the mounts have plenty of meat for that. ill see what the machine shop recomends
     
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  10. DTARS

    DTARS Member

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    finished drilling and tapping my heads for the 7/16 studs.


    [​IMG]


    [​IMG]
     
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  11. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    What kind of rockers are they?
     
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  12. DTARS

    DTARS Member

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    7/16ths roller rockers forgot what brand tho
     
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  13. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    You sure they aren't stud mounted rockers? Those heads were designed to accept pedestal mounted rocker arms.
     
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  14. DTARS

    DTARS Member

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    yes they are stud mounted rockers, im going to be using guide plates with them, why am i doing this, no clue figure id be different and not use pedestal rockers lol well that and i didnt want to spend 200+ on them either lol
     
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  15. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    In that case, you'd better get them to the machine shop. It's not as easy as just drilling and tapping the holes and screwing the studs. You have to machine down the pedestals approx 0.25-0.30 as well. You'll also need to run hardened pushrods not too.

    That's why most don't bother. For the cost and trouble involved in the conversion, you're better off running pedestal mounted rocker arms from the get go.

    ....but, you're this far now. :D
     
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  16. DTARS

    DTARS Member

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    oops lol. oh well ill just have my friend mill them , but first ill see how it fits up with the pushrod gauge . what is the reason for milling off 0.25-0.30
     
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  17. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    To retain the proper installed height. I just did a quick search. I was off with my numbers a tad. .230- .250 is what most cut. I'd shoot for right in the middle.

    [​IMG]
     
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  18. DTARS

    DTARS Member

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    im wondering what will happen if i dont mill off .230-250.

    is it just for clearence to the valve cover, or for it to function properly

    ill see how it compares to the stock pedestal rocker .

    if not a angle grinder and caliper and some fine line tape should suffice lmao j/k
     
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  19. Gearbanger 101

    Gearbanger 101 Straight Outta Locash Super Mod

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    If you don't mill down the pedestal, your pushrods are going to be way too short and you'll most certainly make contact with the valve covers.
     
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  20. DTARS

    DTARS Member

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