Re: Broken Rocker
[Re: Sledge_57]
#2787964
06/22/20 05:46 AM
06/22/20 05:46 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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That’s a geometry issue. He may have too many threads showing on the adjuster, but that didn’t cause the failure. Also, if he machined the spring pockets for clearance that will cause a failure. That goes back to incorrect geometry.
Have him go to b3racingengines.com and read all the tech threads and then have him order a geometry correction kit.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Broken Rocker
[Re: Sledge_57]
#2788007
06/22/20 09:54 AM
06/22/20 09:54 AM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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Thread count that matters: below the rocker, not above. It affects the rocker ratio, smallest thread count is generally higher ratio (not to mention less breakage). Always check for relief clearance machined into bottom of the valve (long) lever where adjacent to spring collar. If you have to do this, after reaching minimum safe depth, radius & blend the relief into the parent body. If it catches your fingernail, that's where it will break.
Boffin Emeritus
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Re: Broken Rocker
[Re: madscientist]
#2788045
06/22/20 11:58 AM
06/22/20 11:58 AM
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Joined: Jan 2005
Posts: 2,540 Milwaukee WI
TRENDZ
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master
Joined: Jan 2005
Posts: 2,540
Milwaukee WI
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That’s a geometry issue. He may have too many threads showing on the adjuster, but that didn’t cause the failure. Also, if he machined the spring pockets for clearance that will cause a failure. That goes back to incorrect geometry.
Have him go to b3racingengines.com and read all the tech threads and then have him order a geometry correction kit. This.
"use it 'till it breaks, replace as needed"
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Re: Broken Rocker
[Re: Sledge_57]
#2788058
06/22/20 12:10 PM
06/22/20 12:10 PM
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Joined: Nov 2011
Posts: 291 PA
Harry's Taxi 2
enthusiast
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enthusiast
Joined: Nov 2011
Posts: 291
PA
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Without seeing the underside of the rocker, everything is just a guess.....could be as simple as the pushrod was too long and adjuster stud was backed out far enough that the pushrod cup hit the underside of the rocker.
'86 Maple Grove KOS Mopar low qualifier......true street legal with no power adders.
NOS-used when losing since 1940.
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Re: Broken Rocker
[Re: Harry's Taxi 2]
#2788059
06/22/20 12:11 PM
06/22/20 12:11 PM
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Joined: Nov 2007
Posts: 21,909 Kirkland, Washington
Pacnorthcuda
Too Many Posts
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Too Many Posts
Joined: Nov 2007
Posts: 21,909
Kirkland, Washington
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Without seeing the underside of the rocker, everything is just a guess.....could be as simple as the pushrod was too long and adjuster stud was backed out far enough that the pushrod cup hit the underside of the rocker. Yep.
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Re: Broken Rocker
[Re: rickraw]
#2788067
06/22/20 12:37 PM
06/22/20 12:37 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,531
So. Burlington, Vt.
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I’m not at all sure of this, but I believe the “-02” on the rocker is the year of manufacture.
If so, we have a broken aluminum rocker that’s 18 years old.
Not really a surprise imo.
Edit- apparently the letters/symbols on the left indicate the year of manufacture, and the number on the right is the month. So, if you don’t have the legend for the letters/symbols...... you don’t know when they were made.
Looks like at least two different years by the pic. “B” on some rockers, “#” on others.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Broken Rocker
[Re: polyspheric]
#2788167
06/22/20 05:00 PM
06/22/20 05:00 PM
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Joined: Jan 2003
Posts: 18,025 S.E. Michigan
ZIPPY
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,025
S.E. Michigan
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Thread count that matters: below the rocker, not above. . What he said!
Rich H.
Esse Quam Videri
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Re: Broken Rocker
[Re: Sledge_57]
#2788203
06/22/20 06:39 PM
06/22/20 06:39 PM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,219
New York
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As said, aluminum will fail eventually. Steel can be run closer to its tensile limit (stretch is what breaks them, not power) and recover. However: the calculation is complex. I'll leave out shape, metallurgy, heat treat, etc. It's the number of cycles × some exponent of the highest RPM reached × spring pressure × some function of maximum incline angle × reciprocating load. An aluminum rocker may last 50,000 miles turning 5,000 RPM, and explode if run to 8,000 even once. Generally true for connecting rods also.
If you can't find a better answer to "what broke it", safest position: assume it's fatigue and replace all of them. Once you get up on the learning curve you'll find that your vision works very well (shade tree FEA) in determining "there should be more metal here", and "that makes me nervous".
Boffin Emeritus
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Re: Broken Rocker
[Re: ZIPPY]
#2788275
06/22/20 10:08 PM
06/22/20 10:08 PM
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Joined: Nov 2003
Posts: 4,027 Dearborn Hts, MI
Sledge_57
OP
master
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OP
master
Joined: Nov 2003
Posts: 4,027
Dearborn Hts, MI
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Thread count that matters: below the rocker, not above. . What he said! Hi Rich, yes I know but on my arms if I had that much thread on top, the cup would be inside the arm... I asked him when the motor was built, no idea yet if this is a recent build or has a lot of time on it... Hopefully he'll answer tonight. Thanks, everyone. EDIT... Just heard from him, 1st: rockers are 20 year's old 2nd:"Had to get some long pushrods about 4 years ago so the adjusters didn't go so far down. The threaded part of the adjustment screw is in the the full body of the rocker. Had a problem before with the adjuster ball end being too low and the cup not receiving enough splash from the rocker oil hole to keep it lubricated, that's why we chose the longer pushrods a few years back." Bad deal all around it sounds like...
Last edited by Sledge_57; 06/22/20 10:27 PM.
Doug
1967 "Pedal Car" 500" low deck , TF 727, 4.30 Locker Best to Date: 11.67 @ 114.9 1.64 60ft
"Kids in cars cause accidents. Accidents in cars cause kids..."
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