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Rocker arms

  1. #1
    Retired Air Force Master Sergeant's Avatar
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    Default Rocker arms

    one of my crane aluminum gold rocker arms broke and I am wondering if they are not strong enough for my mechanical roller cam w/ .670 lift at 6500 RPM? If not what would be a good substitute?

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    Senior Member EVILFORCE's Avatar
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    Quote Originally Posted by Master Sergeant View Post
    one of my crane aluminum gold rocker arms broke and I am wondering if they are not strong enough for my mechanical roller cam w/ .670 lift at 6500 RPM? If not what would be a good substitute?
    How old were they? I am using the Scorpion parts. American made and fair price. Your Golds should be good for that. Might check you geometry for improper alignment.
    No Fool Like A Old Fool is there?

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    NEVER EVER had a problem with CROWERS at same lift and rpm, and had
    them for 10 years!

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    how's the adjustment ?
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    Quote Originally Posted by Master Sergeant View Post
    one of my crane aluminum gold rocker arms broke and I am wondering if they are not strong enough for my mechanical roller cam w/ .670 lift at 6500 RPM? If not what would be a good substitute?
    Were did it break and how are the rest. I have ran Crane in the past and never had a problem. I am Just curious. I now have set of scorpions on my boat and they seem to be holding-up fine. But defining were the break is might help in the "why". M

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    gn7
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    All alum rockers have a life span. Any one that thinks they don't is just kidding themselves. So the first thing I would have to ask is how old they are. If they are not that old, then I would question the rocker geometry. Cranes are as strong as most of the alum rockers out there with the big exception being Isky's monster rocker.

    When they break on the valve side of the trunnion,is almost always fatigue. If it breaks out under the trunnion, it can be overloading or fatigue but it can also be sloppy bearings or extented periods of overly loose lash. If you think about the action of a stud mounted rocker, the lash has exactly the same effect as a sloppy bearing. The rocker body has no idea where the slop is, except that it is at the trunnion. Just another reason shaft rockers are superior to stud. Stud rockers are nothing more than little jack hammers.



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    Senior Member ol guy's Avatar
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    GN-7. There are so many variables on why a rocker breaks, it's beyond countable. IMLAO M

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    gn7
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    I agree completely. Which is why the first thing I would want to know is how old they are, and the velocity of the cam in question. I don't think he is playing with that quick of a cam. If they have had zero issues for some time I would tend to think they were just done.



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    Senior Member ol guy's Avatar
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    Very well could be. BUT any other part issues? ALOT of valve train parts. over-rev,stuck valve, valve float due to weak spring,busted spring, push-rod, could cause such problems. Age of the rocker really shouldn't be the main focus here as much as the "WHY" ! 6500 rpm! The reason bothers me more than replacment. Also I deffinetly agree if they are older than dirt, could very well be a case of "old age". But my dumb-ass wants to know why before replacing them for another possible failure from a new set. IMLAO M

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    i ran one set of crane golds for 20 years, last 7 with a cam that's just a bit more agressive than the op's. 3 years ago, broke one across the trunion. sometimes stuff happens. replaced all of 'em with new crane golds, looking for another 20 years outta these...

    you do have a stud girdle on this thing, right????

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    They came with the engine when I bought the boat about 5 years ago so I am sure they were old. It broke on the bottom half of the trunion, on one side but not the other. No, I do not have a stud girdle.

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    gn7
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    I'd take them all off and keep em for spares. New Scorpions are cheap compared to a wrecked weekend. Keep one or two with you when your go out and your prepared. If you want to stay with Crane, and they are decent rockers, Teague still has some and the price is decent.

    One thing many should keep in mind is, Crane knew the short comings of these rockers in more severe use. Or they would have never came out with its big brother, the wide body rockers. And even those pale in the shadow of an Isky. Those things are flat huge.



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    Quote Originally Posted by Master Sergeant View Post
    They came with the engine when I bought the boat about 5 years ago so I am sure they were old. It broke on the bottom half of the trunion, on one side but not the other. No, I do not have a stud girdle.
    i'm not disagreeing with what gn is saying. what i will say is that the crane golds i had were 20 years old, and had been in service for all but about 2 years of that time. i decided to replace like for like, rather than go to a shaft mount sportsman deal, because that would have involved re-evaluating valve train alignment, new pushrods, etc.
    when mine broke 2 1/2 years ago, i didn't have a spare and could only find one other guy at the track still using them. and he had a spare. i'll never speak bad of him, even though others take their potshots.... pretty much everybody else is running some type of shaft mount.
    now, i carry a spare along with a lot of other spare stuff. the cam i'm running is substantially more aggressive than yours. as far as the golds go, what i'm doing with them is probably on the edge, but the thing's made hundreds of passes since then and everything still looks great. it's all a big test...

    i've also broken an arp stud, sometime before i broke the rocker. we replaced 'em all with new ones, and i carry spare studs. i still think that was my fault, but digressing. i don't know why gn didn't say anything, but you are in the range where a stud girdle is not a bad idea. even with arp's, deflect them enough times and they can break, plus other things can be affected. regardless what rockers you choose to go with, a girdle isn't a bad idea.
    Last edited by bp298; 11-16-2010 at 01:16 PM.

  16. #14
    gn7
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    Quote Originally Posted by bp298 View Post
    i don't know why gn didn't say anything, but you are in the range where a stud girdle is not a bad idea. even with arp's, deflect them enough times and they can break, plus other things can be affected. regardless what rockers you choose to go with, a girdle isn't a bad idea.
    I pretty much agree. I didn't bring in the girdle only because he didn't break a stud. Not saying he can't use one. But most likely played no role in the rocker breaking. I am all for girdles on flat tappet hydraulics I have gotten away from all that myself as well. But a girdle never hurt anything except a wallet and a little more time during lashing.



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