MeanWS6

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?

santino04

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

wrencher

iTrader: (2)

If everything moves freely then, I'd agree in that the spring broke & in doing so maybe the coils bound up then broke the rocker.

Taspeed

iTrader: (1)

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.

Lost

iTrader: (2)

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!

racecar

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.

WAGE_SLAVE

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