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Rocker Arm Dilemma

Discussion in 'Performance' started by renardk764, Dec 22, 2014.

  1. renardk764

    renardk764 New Member

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    I have a 390 Stroker that I'm trying to complete. I've ran into a problem with the EQ Iron Ram Heads (1.92/1.60 valves). Due to the cam, Odessa Heads installed .100 Valves and stronger springs. I purchased Hughes 1555 Aluminum pedestal mounted shaft rockers for the heads. These rockers are designed for stock valve stem lengths, are only adjustable on the pushrod end, and thus geometry is off. Installed without shims the rockers ride on the outside edge of the valve stems. Playing around, it takes .240" of shims to correct the positioning. This seems like an awful lot of shims and I'm hesitant about moving forward. Should I replace the Hughes rockers with adjustable stud mounted ones? Or should I shim the Hughes rockers and move forward? or third option is finding bee hive springs with required seat pressures and stock valve stem lengths. Thanks for any input.
    Engine Spec: [​IMG]

    Cam Spec: [​IMG]

    Hughes Rocker Installed: [​IMG]

    Thanks for any help.
     
  2. dana44

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    You are talking about shimming the rocker pedistal up .240? What is going on with the pushrod side of things? It appears the pushrods need to be lengthened to get the rockers into the proper angle after you shim the base up where it belongs for the proper rocker arm angle. If you shim underneath the pushrods are going to be too short anyway, there is only so much adjustment you can do. Given that much shim, I would get longer grade 10 bolts (stud and nut would be best) to replace the stock bolts on top of everything else, along with longer pushrods. The cam grind itself is least likely the culprit, most likely the pedistals themselves.
     
  3. renardk764

    renardk764 New Member

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    Understood on the pushrod length. Thanks for the tip on grade 10 hardware. Will do. It's definitely a pedestal issue. Thanks dana44!
     
  4. GLHS60

    GLHS60 Well-Known Member

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    Here is a great link concerning pushrod length and rocker arms.

    Thanks
    Randy


     
  5. tazdevil

    tazdevil Member

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    Maybe the best tech presentation this year. Excellent.
     
  6. MoparDanno

    Level III Supporter

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    I have had to shim Harland Sharp/Hughes style rockers on Magnum heads before, I used pre packaged ARP washers between the pedestal and the mount boss and got them where they needed to be. As noted, you will have to lengthen the pushrod accordingly. There is enough bolt length in the Hex bolts for the hold downs that you dont have to really worry about 2 less thread engagement that will result.

    Before you fire that thing, make sure those heads have bronze guides or sleeves in them. EQ's have been having some major issues with the non sleeved heads over the past few years... I have a friend that recently lost a motor because of this issue. Just an FYI.
     
  7. renardk764

    renardk764 New Member

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    Perfect. I'm using prepackaged arp washers also. 2 of the .120" thick for each rocker. I'll check the guides. Thanks.
     
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  8. dana44

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    Yeah, and according to the video, which was a good tutorial, the shimming under the rocker pedistal is where the adjustment goes to give that 90 degree angle they talk about. Thing is, if you have adjustable studs, the pushrods then should have pushrod guides (which bolt under the rockers to start with, that raise the rockers a whole lot (they are about .120 thick, maybe more), which if you have/had them, raise them to the almost proper height to begin with.
     
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  9. MoparDanno

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    Those particular rockers dont have guideplates. They use a rod between the two rocker pivot points to keep them oriented correctly. Think of it as a shaft rocker for one cyl at a time. The hold down bolts are just Allen bolts that bolt through the rocker center and the pedestals set the rocker height/geometry. Often incorrectly... lol.

    This gets really fun when you have Jesel or T&D rockers on the Magnum heads.... You have to shim the whole mount bar up.
     
  10. MoparDanno

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    Exactly what I used. Good luck! And dont hesitate to holler about any other Magnum specific questions.
     
  11. MoparDanno

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    oh!

    Make sure that the washers you are using for spacing are the same OD as the pedestal. If not, you will place more stress on the hold down hardware. The ID is less important, but as you are tightening them down, make sure they stay lined up with the upper pedestal.
     
  12. dana44

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    Yeah, that comment was more for the video. I do prefer the center adjustable rockers, something that can't be done with the rocker rails on Mopar LA blocks, and center adjustable rockers (do they actually make them for Mopars, other than the proper ratio and length for another engine, like big block Chevy, I think), it would be best to have the pushrod guide plates used.
     
  13. renardk764

    renardk764 New Member

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    Will do
     
  14. MoparDanno

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    Only problem with the center adjust setup on the Magnums is 5/16" base thread which really is puny, especially if you start throwing some ramp rate at it. There are people that make stud girdles for the Magnum head ( Jomar ) but by the time you are into good rockers, stud girdles etc etc, just spend the money and go T&D or Jesel. They install SO much nicer.

    Now for the casual guy who isnt pushing .650 or more lift, the Harland Sharp's are my go to choice, because they are a more stable setup than the other stud mount varieties because the base of the pedestal is as large as the mount boss. Does it make it a PITA to setup the rocker adjustment? Yeah, but there are a few ways around that too. :)
     
  15. dana44

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    Well, I figure if the valvetrain was being upgraded from stock, drill and tapping of the bosses to 3/8ths or 7/16ths would be warranted anyway, but that is just me.
     
  16. MoparDanno

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    There is not enough material on the iron heads to upsize the bolts without compromising the integrity of the rocker bosses. The aluminum heads like the Eddies have enough material to upsize to 7/16 with no issues.
     
  17. renardk764

    renardk764 New Member

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    This is my first ever build so I've been researching and learning like crazy. I cheated a bit and had Mike at MRL Performance build the short block. This rocker arm thing through me for a loop. There's all kinds of competing opinions on stud mounted vs shaft mounted rocker arms out there. As well as how to determine proper valve train geometry. So I'm going to try to use the method referenced in the video, but I will have to modify it a bit due to the mechanics of the pedestal mount vs the stud mount.

    These rocker arms have a 1.65 ratio. The CAM card reference is 1.5. I divided the intake and exhaust lift by 1.5 then multiplied the result by 1.65. This gives me a gross lift of .583 IN and .5885 EX. Dividing those results by 2 shows IN mid lift of 0.2915 / EX mid lift 0.29425.

    Do I need to worry about the .00275 difference when shimming the pedestals? I'm pretty sure the pre-load adjustment nuts on the rockers will be able to compensate for the (i'm guessing) difference in push-rod length.
     
  18. dana44

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    When they show the turning of the adjustment nut for the raising of the rocker, you have to do that with the bolt/nut, and then measure the distance to get the angle and shim the underside of the rocker to get the rocker at the proper angle, then determine whether or not the pushrod adjuster is going to be too far extended to make the pushrods fit. Although you can make a decent adjustment with the rocker, you want to clear the rocker underside to make clearance to the pushrod end, but not so much clearance that the adjustment prevents the locking nut not use all its threads to tighten (hope that makes sense). It may take a couple shim adjustments (stacking different thickness washers) to get things adjusted, and once that is determined to be within about .020-.050, then have one shim that thickness for all the rockers, don't stack shims under the rocker pedistal, make it one shim only.
     
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  19. renardk764

    renardk764 New Member

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    Understood. Thanks
     
  20. MoparNorm

    MoparNorm Active Jeeper
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    Ditto, the Harlan Sharp rollers are...well...sharp!:cool:
     
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