Rocker Arm Help

Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by foureyefox347, Nov 21, 2013.


  1. foureyefox347

    foureyefox347 Member

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    Ok so I build a 347 and I put ported gt40p heads on and I have a tfs stage 1 cam. now I want to put 1.7 ratio roller rockers so if I gave out the specs of the pistions and the heads is there anyway for me to check or calculate if the valves will hit the piston with out taking that heads back off
    #1
  2. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    This is something that has to be checked. How would you know if you had .001 or .100 of clearance without checking? The deck height on every block is different among other things. Check to know or cross your fingers and go, up to you :)
    #2
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  3. liljoe07

    liljoe07 Active Member

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    X2

    Not to mention the various other things that can be off as well. There are lots of tolerances that can swing either way and stack up against you, or for you. That being said, you can do it with the heads on if you have the right tools.
    #3
  4. mikestang63

    mikestang63 Mustang Master

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    Better to check now that risk major damage later. As mentioned, every block and heads are different and things like
    Block deck height
    Head deck thickness
    Head gasket thickness
    Rocker arm ratio
    Cam grind tolerances
    Cam timing
    Cam bore alignment
    Main bore alignment
    Crankshaft throw tolerances
    Crank journal tolerances
    Piston wrist pin tolerances
    Connecting rod tolerances
    Valve spring height
    Bearing clearances
    Push rod length

    .... well you get the idea.... all impact PTV clearance

    Method with head off- preferred

    http://www.enginelabs.com/engine-tech/engine-blueprinting-how-to-check-piston-to-valve-clearance/

    Method with head on

    http://www.cranecams.com/faqview.php?s_id=24
    Last edited: Nov 22, 2013
    #4
  5. foureyefox347

    foureyefox347 Member

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    well it looks like the heads are comin off again
    #5
  6. tpstang

    tpstang New Member

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    I have the same situation now, because I just bought a set of heads and want to run trick flow cam. ptv was the biggest question I was dealing with but gave in to pulling the engine down because it just isn't worth the risk.
    #6
  7. Dave2000GT

    Dave2000GT Active Member

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    I'd just let it ride, should be fine.
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  8. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    You buying his valves or something? This is terrible advice!!!!
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  9. mikestang63

    mikestang63 Mustang Master

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    Just wow. I would say that makes the top 10 for 2013 of bad advice.

    tfs1 cam that has the following specs

    Duration @ .050" (degrees) - 221 intake/225 exhaust
    Cam Lift (intake/exhaust) - .312"/.319"
    Lift w/ 1.6 rocker (intake/exhaust) - .499"/.510"
    Lobe seperation (degrees) - 112°

    vs. the stock cam with the following specs
    Duration @ .050 210intake /210 exhaust
    Lift with 1.6 rockers 444/.444
    Lobe seperation 115 degrees

    So take the new lift with the 1.7 RR is
    Intake (.499/1.6) x 1.7 =.530 lift
    Exhaust (.510/1.6) x 1.7 = .542 lift

    Although peak lift has nothing to do with PTV, the increased overlap of the cam and the RR will. With a longer duration and shorter lobe seperation . General rule of thumb is .080" on the intake side, and .100" on the exhaust side. I'd also be making sure his springs are good enough for this lift.
    #9
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  10. 84Ttop

    84Ttop They make new pistons every day, so why worry? SN Certified Technician Mod Dude

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    So with the year coming to an end do we make an official Bad advice of 2013 thread? Just curious..
    #10
  11. mikestang63

    mikestang63 Mustang Master

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    @Noobz347 .. top 10 worst advice of 2013 thread? maybe a sticky? lol
    #11
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  12. Noobz347

    Noobz347 Stangnet Facilities Maint Tech... Er... Janitor Admin Dude

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    This ^^^

    Please don't run the motor until the clearance check is performed. It seems like a pain in the ass if you've never done it before, but it's really a fairly simple procedure.



    Unless... You're into pain and just wanna see what happens when things wrong. :nonono:
    #12
  13. Dave2000GT

    Dave2000GT Active Member

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    They make new pistons every day, so why worry?
    #13
  14. mikestang63

    mikestang63 Mustang Master

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    [​IMG]
    #14
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  15. A5literMan

    A5literMan Mustang Master

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  16. liljoe07

    liljoe07 Active Member

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    Hehe..... All of the above!
    #16
  17. foureyefox347

    foureyefox347 Member

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    yea im pretty sure my springs are rated for that lift and duration i got the alexs parts gt40p springs they say good for .560 lift
    #17
  18. Grabbin' Asphalt

    Grabbin' Asphalt Mustang Master

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    Lmao:rlaugh:bad advice thread would be Great!!!
    #18

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