Rocker arms for 408 build

Small Block Mopar Engine

  1. nm9stheham

    nm9stheham Well-Known Member

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    That makes sense, considering all of the force from both pushrod and valve spring has to go onto just the 2 ears of the pedestal. Time for a grinder if you wanted to remove some of the pedestal height.
     
  2. B3RE

    B3RE B³ Racing Engines

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    This is a little misleading. I didn't have a suggestion for a rocker that would be the correct length for the RHS/INDY head, when the geometry is correct. A centered pattern can usually be achieved by running a pushrod that is way too short, but that isn't good geometry.

    Because the fulcrum to valve centerline is so short on the RHS/INDY heads, most rockers in most applications will be too long. My suggestion, for it to be right, was that the studs would need to be relocated so the roller tip would stay reasonably centered on the valve tip, when the correct fulcrum height for correct geometry was established, via the correct length pushrod. I just don't know of any rockers that will meet that requirement without remachining the heads. If there was a rocker that short currently available, you wouldn't be able to fit anything bigger than a beehive spring in the head without hitting the rocker. The only other option that "might" work, is if Crower will make a set of offset trunnion rockers for you. Be prepared to pay dearly for them, though.

    Correcting geometry is an involved process, and I try to make it as painless as possible with my LA kits, but on a Magnum, more work is involved, and it completely wipes out any savings by being able to use inexpensive stud mount parts.
     
  3. Idaho

    Idaho FABO Gold Member FABO Gold Member

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    LA heads on magnum block

    The block can be drilled to provide oiling for LA heads. It's been done with piping. I read on a circle track forum some had done this and rigged a shaft on Magnum heads.
    The challenge would be doing it for less $$/time/effort than what the Hughes shaft system goes for ($760).
     
  4. Idaho

    Idaho FABO Gold Member FABO Gold Member

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    Thanks for the clarification. I think you have clarified that you do not have a viable suggestion for rocker arms on Magnum heads.
     
  5. Wyrmrider

    Wyrmrider FABO Gold Member FABO Gold Member

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    i've relocated lots of studs
    bbc rockers in sbc and all that
    pita
    magnum heads have little to work with
    Crower set back fulcrum rockers are where to start
    what your current and target distence from the center of the fulcrum to the center of the roller with the valve at half lift
    you can get a piece of 3/8 sqaure or hex
    lock the valve at half klft with a screw c-clamp on a seal
    put te stock in the tip
    then top of the stock is a line were the fulcrum has to be
    then take a piece of 5/16 rod with a round end and sit it in the lifter at top lift
    where where the two cross
    that's as short as your adjuster side can be without hitting
    do the same on the base circle to find the longest
    now do some calcs and grind if you need to
    now set you're cam and lifter at mid lift because that's the line your adjuster is going to be on
    now find a rocker that fits and put your stud or shaft there
    good luck finding a rocker where the adjuster is in line with the pushrod at mid lift
    obviously if is nit your ratio changes with adjustment and there is more stress
    yoy may just have to get the center of the adjuster ball line to the center of fulcrum perpendicular to the pushrod line then get your pushrods to put the ball where the two lines intersect
    you do not want a lot of threads showing especially if the adjuster is not in close alignment with the pushrod
    funfact the rocker stud is not in line with the valve stock
    is now after customer came back and wanted to run a taller spring/ longer valve
    btw hate short arm rockers use stock low ratio rockers and set up mid lift perfect or sell the heads
    now cad and 3d printing
     
  6. B3RE

    B3RE B³ Racing Engines

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    That is true, and neither does anyone else if they want correct geometry. That rocker doesn't exist, as I mentioned in my previous post. I can put just about any rocker on a head, as long as it will fit under the valve cover. Where it is located on the head is the key to proper geometry and operation.

    I've done corrections to these heads using the shortest rockers I could find, and they still needed the studs relocated. The offset trunnions are the only thing that might work. I have viable options, but a bolt on rocker isn't one of them if it's going to be right.
     
  7. rumblefish360

    rumblefish360 So close, yet so far away FABO Gold Member

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    Such a PIA this can be huh?
     
  8. 12many

    12many Well-Known Member

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    For a street cruiser with a 5800 rpm target and lift of .525” max, doing stud relocation and/or using other specialized components, or any combination of fixes, is this common, recommended, something you or others well versed in these things advise and do as a matter of course? Seems to be way overkill in this case. Sure, if one wants to do that by all means, but using factory or the MP rocker setup? One would think at this level just using quality components, correct length pushrods and good assembly is all that is required?
     
  9. B3RE

    B3RE B³ Racing Engines

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    If stock rockers and stock length valves are used, it should be fine. But, if it's good enough for a roller rocker, it's good enough to have good geometry. That roller tip changes the geometry so drastically, I won't let anything leave the shop without being corrected. I will recommend a stock rocker on a mild build every time, if the customer isn't willing to make the necessary corrections for a roller rocker. So, yes, it is common, and a matter of course in my shop. I've seen too many broken parts to want that liability on anything I build.
     
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    • B3RE

      B3RE B³ Racing Engines

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      Also, correct length pushrods means raising the roller rocker so high that the roller is about to run off the valve tip. The only fix, move the studs to bring the roller back to the center of the valve stem.
       
    • JunkyJimmy

      JunkyJimmy FABO Gold Member FABO Gold Member

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      I was all worried about the rockers on the first mag I did, I'm now running fairly close to rpm and lift as I did in the 80's with roller cam and w-2 heads on core motor used rockers and fulcrum. Honestly, it isn't pretty but it is the last thing I think about on the car. Pretty flipping impressive for 0 dollars.
       
    • Idaho

      Idaho FABO Gold Member FABO Gold Member

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      I think you are basically agreeing with what I have suggested in post #62?

      Everything I'm seeing suggests there is a threshold where the upgrade makes sense.

      Lift over .525.
      High spring load (over 350? not sure.)
      High revs, especially continuous.
      Desire/need for small horsepower gains.


      I am curious to know what you have seen typically breaking.
      Also, what would be typical cost to have rollers done to your satisfaction?
       
    • Idaho

      Idaho FABO Gold Member FABO Gold Member

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      Holding one in my hand, it kinda grows on me. Not a bad piece of hardware. I think they get a bad rap. :)
       
    • B3RE

      B3RE B³ Racing Engines

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      Mostly I have seen the fulcrum split wide open, but I've also seen broken adjusters, the tail end broken completely off the rocker, threads ripped out of the rocker body when the adjuster was punched out of the rocker body, broken roller axles, etc. etc.

      Rockers aside, you can include dropped valves from locks unlocking, or pulling through the retainers, broken valve springs, valve heads breaking off. Some off these are extreme cases, but any part will break if you take a jackhammer to it long enough. That is the effect of an unstable valvetrain from incorrect geometry.

      High quality parts are not immune to a lack of attention to detail. The best NASCAR connecting rods will let a bearing spin and will be destroyed, if there is inadequate bearing clearance. I know what you are saying, "I would never put an engine together without checking bearing clearance". Ok, now replace "bearing clearance" with "rocker geometry". Now we're on the same page.

      As far as cost, I won't discuss that here. There are too many variables to consider, so it would be best to call so I can get the information needed to do an estimate.
       
    • nm9stheham

      nm9stheham Well-Known Member

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      Have replaced a few broken stock type rocker parts from hard use. In each case it was one piece that was weaker than the rest and let go. We don't have the means in the field to detect these. So we just run them and hopefully find the weak unit and can replace it without too much associated carnage. More often than not, breaking rockers are just that.

      Story: Broke a spindle in a rally. The wheel was just laying there LOL. The spindle casting had a void in the middle that finally allows a crack to start. Had thousands of racing miles on it. I did not stop using stock spindles.

      All this is good discussion.
       
      Last edited: Feb 3, 2020
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      • Moparhead

        Moparhead Well-Known Member

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        I love stock rockers! My buddy has the 525 cam in a 360! Worked well with stock rockers! I’ve only had one push rod go up threw my rocker one time in 7 seasons lots of miles there bad ass and reliable!
         
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        • Idaho

          Idaho FABO Gold Member FABO Gold Member

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          Just a visual to demonstrate the rotational limits of the stock rockers.
          Perhaps a high lift cam may approach the limit and certainly would destroy the fulcrum. Or perhaps high spring pressure and the jackhammer effect.

          B1E3B99F-DACF-4BFD-A1D8-11E76566E65A.jpeg

          395E7F38-372A-4F27-9532-37FA163E83D3.jpeg

          253D959E-F5D0-421F-96A8-A070312969AA.jpeg
           
          Last edited: Feb 3, 2020
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          • Idaho

            Idaho FABO Gold Member FABO Gold Member

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            Some of the failures you describe are aftermarket, some factory. Care to comment which you see more of?

            Regarding cost, for the sake of those who will utilize the thread I was hoping for a rough ballpark. I'm guessing it would run as much or more than the cost of a Hughes shaft system ($760)?
            No worries if you prefer not to say.
             
            Last edited: Feb 3, 2020
          • Idaho

            Idaho FABO Gold Member FABO Gold Member

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            Another Harland Sharp to consider.
            Kinda unique - pedestal and adjustable on the push rod ball.
            This has appeal. Not cheap but less than the Hughe's shaft system, and correct me if I'm wrong but I think the pedestal makes it stronger than a stud conversion.

            harland sharp pedestal adjustable.png
             
          • nm9stheham

            nm9stheham Well-Known Member

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            The pedestal/spacer does do that in the same way as the stock pedestal. Can't say if it does it as much, or more or less. Interesting that there is a rod between pairs of rockers for each to help stabilize its partner.

            Going to the roller makes the info from B3RE more important.... I would start on the assumption that to the roller changes the geometry situation considerably. The way the roller rolls back and forth across the valve tip is typically quite different than how stamper rocker tip 'walks' across the valve tip.
             
          • Idaho

            Idaho FABO Gold Member FABO Gold Member

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            Interesting. Attractive feature but from what I can see the s70036a does not have the cross shaft.
            The one below does, but is 1.7 and not adjustable. Seems like that would eliminate the need for guide plates.
            To my way of thinking if the roller makes a decent pattern on the valve tip I'd be happy. Kinda seems like a crap shoot with the rollers though.

            harland sharp 1.7 paired.png
             
          • Idaho

            Idaho FABO Gold Member FABO Gold Member

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            Here is the elusive critter. 1.6 ratio, adjustable, tie bar.
            Found in a thread here. User reports "perfect geometry" on RHS heads.
            Might be the new nirvana.
            If they are still making them. I think they are made to order so maybe a wait time.

            Rocker arm rumor???

            harland 1.6 adjustable tie bar.png
             
          • Wyrmrider

            Wyrmrider FABO Gold Member FABO Gold Member

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            where the roller sts on the valve is not important unless it is close to the edge - or off
            narrow stripe is what is important
            roller tip raises the line from trunion to center of roller the radius of the roller from the valve tip
            you just cocked the valve close up about 3/8 of an inch for a 750 dia roller tip and same with valve open
            SNAFU
            you have to raise the fulcrum so that when the valve is at half lift
            a line through the fulcrum and the center of the roller is parallel to the top of the retainer or perpendicular to the valve stem (same thing)
            easy to see with the engine on the stand and a machinist rule held on the fulcrum-roller line
            you may need longer studs
            you will need correct length pushrods
             
            Last edited: Feb 8, 2020
          • Idaho

            Idaho FABO Gold Member FABO Gold Member

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            Reviving this for opinions. I was planning to use stock rockers but just not liking how things look. With a .515 lift cam the rocker tip sits with more angle than I like with the valves closed. With shimming up the pedestal I get too much angle with valves open. What I mean by this is the rocker is making contact with only the valve tip edges at the starting or finishing positions.
            I'm considering these three options.

            PRW steel stud mount rockers (Chevy style). Advantage with polylocks getting nice geometry. Seems weak with 5/16 mounting bolts unless girdle added, requires guideplates. Less expensive. Not sure if they fit under stock valve covers.
            0236006 - Dodge 3.2/5.2/5.9 1.65 x 3/8" for Edlebrock Heads, PRW Stainless Steel Rocker Arms

            Harland Sharp extruded aluminum pedestal rockers.
            Pedestal seems stronger. Pairs on shafts so no guideplates, more stable.
            Nonadjustable fits under standard rockers. $420 (I have significant valve height variability, would have to fuss around with push rod lengths)
            Adjustable version needs taller valve covers or a spacer. $550 plus valve covers or spacer.
            Untitled 1

            I'm kinda leaning to the non-adjustable HS and deal with getting the push rod length right.
            Input appreciated.
             
          • rumblefish360

            rumblefish360 So close, yet so far away FABO Gold Member

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