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  1. #1
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    Default Valve Stem Mod to stop valve drop in chamber

    I just had a PAC Beehive spring break - #4 cyl exhaust on a TFS 11R 190 head on a SBF 363 stroker. Luckily no collateral damage. Not sure what caused it. PAC dealer says these springs are designed for high RPM and anything lower than 3K causes issues, as they are not in optimal frequency like driving around town normally or highway cruising. Im kinda not buying it. Car is used predominantly for racing speed events and Targa, but it is street registered and do drive it on the street.

    Im replacing them with full new set to start a fresh, even though motor hasn't done a lot of work.

    Beehive theory is great (lower weight, better spring design) The one thing that spooks me with them is if ones breaks nothing to prevent valve dropping in like a dual can (still limited I know, but there is a safety net there).

    But anyhow...I was thinking would there be anyway to slide on a brass or copper collar 1-1.5mm above guides, to act as a stopper on the valve going into chamber if the spring does fail. Obviously loss of power and a bit of a racket from floppy spring, but these could be the tell-tale signs to shut down. Most (if not all) collateral damage is from that darn valve dropping into chamber.

    Putting it on might prove to be problematic, as obviously go to be done when valve in head, but something like a soft brass or copper or alloy sleeve, with low resistance (ie, easily slide over valve shaft and easily removed). Could be secured by very small amount high quality epoxy (similar to jb weld). I woud do the job this time with head still on. Remving the valve could be a PITA but would cross that bridge when get to it, and generally when valve needs to come out its a head rebuild anyway.

    Whats everyone thoughts

  2. #2
    Do you ever leave? paulzig's Avatar
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    Thoughts are, you should go to a double spring instead of a beehive..

  3. #3
    Part of the furniture Deuce.'s Avatar
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    Sounds like you need a pin through the stem just under the retainer.
    But seriously, if a broken spring is an expected issue, then as PZ said, stick to duals.
    Can you get ovate wire duals? (Hopefully less resonance issues)

  4. #4
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    Thanks guys for comments.

    Unfortunately kinda committed to the beehives. Of course nothing absolute, but I have invested money into Ti retainers and locators to suit these springs. ($1300 worth inc springs) I would have to re-do whole set-up. They were also recommended by an experienced race engine builder. He's also stumped why the failure. Beehives are better for higher rpm control, but yes, duals have that added safe-guard. The PAC rep reckons low rpm running is not good for these springs, but not buying that quite yet. Im a bit peeved cuase engine hasn't done a lot of work.

    Cam specs (custom).
    Gross Valve Lift - In: 0.585, Ex: 0.582
    Dur @0.50 - In:242, Ex:250
    Lobe Lift - In: 0.3660, Ex: 0.3640
    Lobe Sep - 110


    This is all with Jesel shaft rockers and Morel RPM low pump HYD roller lifters.

  5. #5
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    Damn, this is the first time I've heard of a PAC spring failing like that.

    Out of curiosity, which PAC springs are they?

  6. #6
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    I know, PAC are generally pretty good, the best even (up there with PSI), why the engine builder goes with them. He's pretty picky. Only one failed (cyl#4 on exhaust), but not sure of intregity of others, so changing them all out (at another $500 , and checking them and if all good keep them as spares.

    Not sure of part# but think they are the PAC-1409X 170lb seat, and 420lb open. Spring Rate (lbs/in)
    436 lbs/in. To suit SBF Trickflow 11R 190 head.

    Jesels are 1.6 RR

    but back to the valve collar idea...….
    Last edited by TKFD; 22-07-2018 at 09:36 PM. Reason: error

  7. #7
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    The collar could work. Maybe heat them up and shrink them on just above the guide at full lift.
    If the spring fails and the valve drops to the collar it would still get hit by the piston, I assume?

  8. #8
    Do you ever leave? paulzig's Avatar
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    Check retainer to guide/seal clearance 1st. Were the springs set up the correct distance from coil bind what does the build sheet say or can you ask builder?

    From PAC springs:


    Specifications

    Part# PAC-1409X
    Name Valve Spring
    Description RPM Series Stock Eliminator Beehive
    OD Large End 1.250
    ID Large End 0.845
    ID Small End 0.650
    Install Height 1.800
    Load at Installed Height 175
    Spring Open Height 1.250
    Spring Open Load 425
    Recommended Valve Lift 0.550
    Spring Rate (lbs/in) 436.000
    Mass (grams) 60.50
    Coil Bind (max) 1.190

    If you are setup at 1.8" installed height with .585 and .582 lift you are only around .025" away from coil bind with tolerances in spring itself,rocker arms and cam lobe lift you might be too close. I'd email PAC and ask if .025 is too close, odds are they would say yes.

  9. #9
    Do you ever leave? EH179's Avatar
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    Good point! you need min' .060" for safe coil bind clearance.

  10. #10
    Do you ever leave? paulzig's Avatar
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    Quote Originally Posted by EH179 View Post
    Good point! you need min' .060" for safe coil bind clearance.
    I dont know where they are actually set up, so just an assumption as it stuck out after I checked the spring specs on the PAC website. Worthy of note though.

  11. #11
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    Thanks paulzig, yea good point. Engine builder checked and all good supposedly. He says he does like to run a tight bind to minimise wave harmonics.


    But anyway, we've decided to go with good quality endurance race LS style duals.
    Last edited by TKFD; 24-07-2018 at 10:05 AM.

  12. #12
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    Quote Originally Posted by RedTaxi View Post
    The collar could work. Maybe heat them up and shrink them on just above the guide at full lift.
    If the spring fails and the valve drops to the collar it would still get hit by the piston, I assume?
    no, I would locate collar 1-1.5mm above the guides at full tilt, so if spring does fail, the valve would sit on the collar. It would run like shit, but that's good as it would be a telltale to shut down.

  13. #13
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    Did you have the correct locators for the spring base? If the base is walking around, that can cause failure. Can also take up 20thou of your installed height if originally measured off the head..

  14. #14
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    Quote Originally Posted by TKFD View Post
    no, I would locate collar 1-1.5mm above the guides at full tilt, so if spring does fail, the valve would sit on the collar. It would run like shit, but that's good as it would be a telltale to shut down.
    But the valve would be sitting on the collar, so the valve would be hanging fully open with the engine still running...

  15. #15
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    IF the valve is relatively the same angle as the piston then it would probably dance up and down on the piston,without bending.
    A Holden v8 would do that to a degree,thats the plan anyway lol!!

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