Broken rocker arms two weekends in a row

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I think it's metal fatigue. And I'm not a fan of roller bearings on the rocker shaft. I always preferred bronze bushings in the rocker arms. But Rod Bloomer has made me a beleaver in the Hughes rocker arms. It's too bad that they don't make them for W series heads.
 
I'm curious if you looked at the shafts or the actual shaft roller bearings and the actual surfaces of the outer bearing race, and the shaft.
If there was brinelling on either surface, that might cause vibration or stress on the rocker.
Can you crack one of the damaged bearings apart to look at the surfaces.
I'm thinking that you just may need to replace the bearings, not the rocker, (shrug) ?
 
Check to see if the pushrod is hitting the head where it goes through the head, sometimes the pushrod will grace the inside of the heads.
 
inertia said:
I'm curious if you looked at the shafts or the actual shaft roller bearings and the actual surfaces of the outer bearing race, and the shaft.
If there was brinelling on either surface, that might cause vibration or stress on the rocker.
Can you crack one of the damaged bearings apart to look at the surfaces.
I'm thinking that you just may need to replace the bearings, not the rocker, (shrug) ?
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The bearings and shafts all looked good, no discoloration or other defects/damage seen.
 
Les Gibson said:
The bearings and shafts all looked good, no discoloration or other defects/damage seen.
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If the needles have worn ridges ( like a worn u-joint, limited motion back and forth created troughs) that the needles recess into, that the initial pressure to get the needle/rocker to move, could be twice the actual force needed to "rock" ? ?
With the extreme spring pressures .
Pic is extreme of my meaning .

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inertia said:
If the needles have worn ridges ( like a worn u-joint, limited motion back and forth created troughs) that the needles recess into, that the initial pressure to get the needle/rocker to move, could be twice the actual force needed to "rock" ? ?
With the extreme spring pressures .
Pic is extreme of my meaning .

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I see where you're going with potential needle bearing issue causing my breakage, but I really don't think it's a contributing factor in my case. The bearings on both broken rockers looked absolutely fine, there was no evidence of any failure at all. I had a couple other racers who are familiar with HS rockers look at them and they both told me they were fine.
 
I would sure like to see a picture of your geometry throughout the lift pattern. Like 6-8 pictures with anything but a flip phone
 
Les Gibson said:
I see where you're going with potential needle bearing issue causing my breakage, but I really don't think it's a contributing factor in my case. The bearings on both broken rockers looked absolutely fine, there was no evidence of any failure at all. I had a couple other racers who are familiar with HS rockers look at them and they both told me they were fine.
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Sure, I always take broken stuff apart to see what/where it failed.
I found it curious that it blasted apart as opposed to just hinging open as others I've seen ,
Good luck .
 
Les Gibson said:
Asking if anyone might have any thoughts on what might be causing this.
For consecutive weeks I've broken an exhaust rocker arm. Last week #4 exhaust rocker broke. This past Friday night #5 exhaust rocker broke. These are Harland Sharp rockers installed on Mopar Performance aluminum W5 heads. There's no oiling issue or clearance issues. I am told by the previous owner of my Arrow that these rockers are about 6 years old. Is this a case that they're just wore out and I need a new set or is there another reason. Appreciate any constructive thoughts.

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Adding to above post the exhaust is your issue so that is what I would like to see. Valve length differences between the intake and exhaust is common. Then you have the heavier thicker valve margin that comes into play. On a single shaft system like Mopars this really has to be though out. Sometimes a simple fix is a lash cap on one or the other.
 
inertia said:
Sure, I always take broken stuff apart to see what/where it failed.
I found it curious that it blasted apart as opposed to just hinging open as other I've seen ,
Good luck .
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I'm with you, I've never seen a rocker arm break like these have. I wish I still had the Norris stainless steel roller rockers that were on my old W2 Dart. But I didn't have a spare set of rockers to swap them out with when I sold that car so the new owner is all set in that regard!
 
pittsburghracer said:
Adding to above post the exhaust is your issue so that is what I would like to see. Valve length differences between the intake and exhaust is common. Then you have the heavier thicker valve margin that comes into play. On a single shaft system like Mopars this really has to be though out. Sometimes a simple fix is a lash cap on one or the other.
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Thanks John, I'll have to look at the documentation that the previous owner gave me on the car. I know he included intake and exhaust valve lengths and diameters, along with spring diameter and spring pressure in the paperwork. I know the gentleman I bought the Arrow from is a pretty darn good engine builder and he told me in the 16 years he and his wife ran the Arrow they broke 4 rocker arms over those years.
 
Les Gibson said:
Thanks John, I'll have to look at the documentation that the previous owner gave me on the car. I know he included intake and exhaust valve lengths and diameters, along with spring diameter and spring pressure in the paperwork. I know the gentleman I bought the Arrow from is a pretty darn good engine builder and he told me in the 16 years he and his wife ran the Arrow they broke 4 rocker arms over those years.
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All exhaust?????
 
Mr. Sinister said:
Must be serviced weekly then….
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Lol. Five years on my last set of springs on a .650 lift solid lifter cam. I didn’t tear those heads apart yet but I may use them again. I have one of those fancy on engine T&D spring pressure testers and it stays at home on a shelf. 7-8 years I’ve probably used it twice.
 
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