keep busting rocker arms
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2004-2007 Cadillac CTS-V Performance Mods Discussion, keep busting rocker arms in Cadillac CTS-V Series Forum - 2004 - 2007; Well, today will be my 4th busted rocker arm.. From no less than 3 unique sets of Yella Terra 1.7 ...
  1. #1
    ichpen's Avatar
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    keep busting rocker arms

    Well, today will be my 4th busted rocker arm.. From no less than 3 unique sets of Yella Terra 1.7 rockers.

    What the hell is going on? It's winter, not pushing the car at all. All 4 have been on different cylinders. Hardened pushrods are fine.


    YT sent me a complete replacement set after the last one where I lost 2 in one go. All in stop and go traffic.

    Mild cam, trickflow 225 ported heads, rest of the stuff in the signature. 7.6 hardened pushrods. Why oh why???

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    darkman's Avatar
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    Re: keep busting rocker arms

    I would go back and try to recheck the basic valve geometry.

    Check the wipe pattern accoss the valves using a set of checking springs so that it is independent of pushrod length.

    Then recheck the pushrod length. The pushrod length sounds long to me as I thought the starting point was closer to 7.500 inches. (Mine came in at 7.375 gauge lenght/7.367 measured overall on my 215s but I had Morel lifters and milled heads.) This, of course, also gets into preload - make sure you are not over preloading and bottoming out the lifter.

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    Re: keep busting rocker arms

    That is a lot of preload.

    What lifters?

    Did you use an adjustable length pushrod to determine length?

    Sounds like the lifters are bottoming out.

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    Re: keep busting rocker arms

    Quote Originally Posted by heavymetals View Post
    That is a lot of preload.

    What lifters?

    Did you use an adjustable length pushrod to determine length?

    Sounds like the lifters are bottoming out.
    How do you know how much preload he is running?

  6. #5
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    Re: keep busting rocker arms

    Stock pushrod is 7.400"

    If he didn't change the lifters and didn't use a thinner head gasket (which would make it worse), the length of pushrod he is claiming to use is bottoming out the lifter.

  7. #6
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    Re: keep busting rocker arms

    Like heavy said, without knowing the rest of the specs like head gasket thickness and stuff Luke that, those pushrods sound like they may be on the long side. That's the first thing I would check.

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    Tmac11 is offline Cadillac Owners Member
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    Re: keep busting rocker arms

    Are the TrickFlow heads using the same valve angle as stock? From my Ford days TrickFlow usually altered the angle necessitating the longer pushrods. But as Heavy said, get an adjustable pushrod and check the lenght.

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    Re: keep busting rocker arms

    Here is some good info:

    http://www.enginebuildermag.com/Arti...l_session.aspx

    Also, if the valves are different, they may have a different length (longer) which will make it worse.

    more good info:

    http://www.popularhotrodding.com/eng...ic_lifter.html

  10. #9
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    Re: keep busting rocker arms

    My first thought is push rod length also. It's easy to pull a valve cover and check. If I'm not mistaken, you had an engine builder assemble your motor, it would probably be a good idea to double check that. None of us can say what the correct length should be for your setup because we don't know if your cam's base circle is changed, head gasket thickness and the trickflows require different length from stock to begin with.

    What are your cam specs? I thought the Trickflows came with different valves and springs that wouldn't allow for higher lifts. They make up for the lower lifts by their geometry. I thought about getting a set for my new motor but didn't want to venture into that territory.

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    Re: keep busting rocker arms

    Hey guys, thanks for the input. I'm running morel lifters. And pushrod is 7.4 not 7.6, typo.

    Cam is 224/232, 112 as measured. Lift .581/.588 as per spec.

    Valve lash intake/exhaust at +0.55. I have my engine build sheet in front so can read out a bunch of fascinating info.

    I'm now thinking it's head geometry/restriction here though my builder cleared it. Or maybe even the springs (TEA Duals) are too much for the YTs. But I'm not running any special combo here which is why I'm confused on it. And it's always a different cylinder that goes meaning the problem is systematic.

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    Re: keep busting rocker arms

    What is the spring rate on the TEA duals?

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    Re: keep busting rocker arms

    .650 max if I remember correctly.

    And I was thinking of going to a more aggressive cam. Pfff.

  14. #13
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    Re: keep busting rocker arms

    Quote Originally Posted by ichpen View Post
    .650 max if I remember correctly.

    And I was thinking of going to a more aggressive cam. Pfff.
    Yeah, I looked your up engine build thread. The open spring pressure on the TEA Duals is 380 lbs. @ 0.0650. That does not look all that high to me, especially since the use of the Yella Terra rocker requires a pretty stiff spring becuase the weight of the roller over the valve. (I am running Comp 921s with an open spring pressure of 400 lbs.)

    I would still check the preload to see if is still at the build sheet spec. (Morels use from 0.030 to 0.050 preload). Having thought about I think you can tell if the "wipe" is okay by just looking at the top of valves. If they are marked across the center with a thin line you are okay.

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    Re: keep busting rocker arms

    According to the build sheet. Int seat pressure open is 425lbs, seat pressure closed is 135. I'll check wipe today when I look at the rocker carnage.

  16. #15
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    Re: keep busting rocker arms

    Hmmm. Looks like you upgraded the spring selection and the lifter selection from those mentioned in the build thread.

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