Rocker arm failure on track
10-09-2018, 07:54 PM
#11
On a dedicated race car, non-VTEC rockers are lighter and their rollers allow a more aggressive cam profile. However, for street use, VTEC allows a very aggressive cam while maintaining street manners and flexibility. 4Piston reported a while ago that the added VTEC back to their 330hp 2L K-series used in an SCCA P1 CN chassis to give the driver added flexibility when they had to deal with traffic situations.
10-10-2018, 08:16 AM
#12
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Thread Starter
On a dedicated race car, non-VTEC rockers are lighter and their rollers allow a more aggressive cam profile. However, for street use, VTEC allows a very aggressive cam while maintaining street manners and flexibility. 4Piston reported a while ago that the added VTEC back to their 330hp 2L K-series used in an SCCA P1 CN chassis to give the driver added flexibility when they had to deal with traffic situations.
10-10-2018, 10:50 PM
#13
Note that these rockers range from $800 (original blue) to $1000 (newer gold). Ferrea makes a purple set for 4Piston, also $1000.
They are really designed for high revs and very aggressive or high-lift cams. For most applications, they are probably overkill.
10-12-2018, 07:52 AM
#14
Could this be from over tight valve lash ?
10-12-2018, 08:27 AM
#15
I guess I have a hard time believing that the rocker failure was the cause, you'd think that if it failed on its own it would not prevent a valve from closing to allow PTV contact as you have the spring pulling the valve back up once there is nothing to press it down.
He has shown that the spark plug has seen something so I guess I am curious if something made its way into the combustion chamber then lead to a valve not being able to open or being stuck open and tagged by a piston. The rocker would break when pressure was applied to the valve that didn't want to move.
It just seems weird to me since the picture he posted shows the retainer / keepers / springs / valve stems seemingly normal.
He has shown that the spark plug has seen something so I guess I am curious if something made its way into the combustion chamber then lead to a valve not being able to open or being stuck open and tagged by a piston. The rocker would break when pressure was applied to the valve that didn't want to move.
It just seems weird to me since the picture he posted shows the retainer / keepers / springs / valve stems seemingly normal.
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Xene (10-13-2018)
10-13-2018, 09:53 AM
#16
To me that spark plug looks like something flat hit it square on the end. The only thing I can think of that would do that is a piston and the only way a piston would make contact with the spark plug is if a wrist pin busted. my theory is that the busted rocker is the result of something worse. I really hope I am wrong, otherwise you will have more to fix than the head.
11-07-2018, 08:38 AM
#17
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Thread Starter
Actually didnt break just one...this came off the intake side of #2 after I got the assembly lifted:
11-07-2018, 08:52 AM
#18
Could it have been simple valve float? Piston contacts the valve forcing up on the rocker, but doesn't seem likely given the rpm stated. Makes me steer more towards the piston contact via broken rod/wristpin. Valvetrain was just a casualty rather then the cause in that case.
11-07-2018, 09:11 AM
#19
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Thread Starter
Could it have been simple valve float? Piston contacts the valve forcing up on the rocker, but doesn't seem likely given the rpm stated. Makes me steer more towards the piston contact via broken rod/wristpin. Valvetrain was just a casualty rather then the cause in that case.
11-07-2018, 09:43 AM
#20
Right, which makes me think your bottom end let go first. You got a motor that cant turn more then 90 degrees. You have a piston that became separated and wedged up against the head crushing the plug and valves on that cylinder. All your valves are in place, none dropped. But if you have a piston sperate from the wrist pin, now its out of time with the valavtrain and wham! Hits the valve when its in the down/open position forcing the valve back up against the rocker wile its trying to go down, not up.That's my theory. Not sure what else it could more likely be.
Last edited by s2000Junky; 11-07-2018 at 09:46 AM.