What can cause a rocker to break? Spring breaking?
Thread Starter
TECH Fanatic
Joined: Nov 2001
Posts: 1,064
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From: CA
What can cause a rocker to break? Spring breaking? I had a stock rocker break on my new motor, want to know what can cause them to break. I have not spun it past 6K and have gone WOT like only 15 times. Wanted to get 1K miles on her before I started running it like a 408 was meant to be run 
So what can cause a rocker to break? Spring breaking? The spring had broke, just want to know if that was the culprit first. Sorta like, what came first - the chicken or the egg; the spring or the rocker?
So what can cause a rocker to break? Spring breaking? The spring had broke, just want to know if that was the culprit first. Sorta like, what came first - the chicken or the egg; the spring or the rocker?
Launching!
Joined: Mar 2004
Posts: 240
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From: Chicago Suburbs
Tough question, for me anyway. Its almost like youd have to be in the motor to see that one. Through reasoning, I would say the spring first, because it must have been under stress and pressure from the rocker pushing it down and it releasing back up. Then I would think the rocker would have broke, possibly from when the spring broke and caused a sharp like jolt to the rocker from releasing its tension. That would be my educated guess, so it may have actually all broke in unison (meaning together at the same time, for the mentally challenged). So I would see it as your running the motor high RPMs lets say, the rocker pushed the spring down, and BAM the spring broke releasing its pressure which jolted the rocker and broke it. 
Sounds Good to me ahaha. If you have an M6 and bounced that sucker off the rev limiter because of a missed shift that definitely would have caused it. Good Luck 
Sounds Good to me ahaha. If you have an M6 and bounced that sucker off the rev limiter because of a missed shift that definitely would have caused it. Good Luck 
probably pretty close if not exactly, but I'd guess maybe the spring height was not set right or something and caused a spring to bind putting excess pressure on the rocker. Breaking both the spring and the rocker. This could happen especially if your using some beefy double springs.
Sounds like you spent a lot of money on this motor, why in the world would your engine builder not recommend a true shaft mounted rocker like Jesel or Comp. With all the failures of stock rockers, spilling needle bearings in stock motors, I wouldn't even think twice about ditching the stock rockers.My personal opinion is that the spring broke, knocked the valve alignment off then the rocker broke. check for a bent valve too!
TECH Resident
Joined: Aug 2004
Posts: 875
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From: Portland Oregon
I would agree with the above. Spring breaks, that the rocker beats it's self to death. If the rocker broke first, the spring may not (??) be damaged. Who knows for sure.
When you put your foot to the floor, you own all of the pieces.
When you put your foot to the floor, you own all of the pieces.
Staging Lane
Joined: Oct 2004
Posts: 73
Likes: 0
I cannot see how a rocker can break without the spring breaking first. So, I would have to say your spring went first then it all snow-balled from here. What springs did you have? Get some Patriot Golds now! My engine builder for my 402 said to keep the stock rockers also
