V6 Donut

Hi everyone! My name is Chase and this last track event I broke a rocker arm. This was my second HPDE on this motor and have driven appx 2000 street miles.

just though id share.

I made 216hp with my stock ap1 motor. burned 0 oil. it was to good to be true.




This was an UP SHIFT, from 3rd to 4th

I was in 3rd gear on the big straight at Texas World Speedway, sun got it my eyes I hit the rev limiter and shifted to 4th and then after shifting to 4th almost immediately I received my WRX conversion and lost Cylinder 4.

Here's the pictures.













No the keeper did not break.








Well, any ideas why this happened?

Fierc3

Subscribed, bc I'm stumped..... wtf

Soviet

Wow.

windhund116

Over rev ---> valve float? Valve spring force wasn't enough to pull valve close. Piston hit valve ---> catastrophic damage to the valve, associated rocker arm, and top of piston.

Or retainer completely failed and let valve drop into combustion chamber? That must have made of HELL of a racket, when it happened.

Sorry about that.

s2000Junky

That is pretty odd. I wonder if the keeper actual fell out for some reason and started the whole chain of events. The top the retainer looks ok, but typically if that does fail a crack is seen from the under side. Is there one? A crack would allow the valve to drop down just far enough to make contact with piston, but usually just bend the valve. Id expect to see the retainer folded up and or missing as well with this much damage. Hard to say here.

windhund116

Looks like over-rev or continuous near-redline RPMs played a role here, too. In terms of the amount of damage done. Keeper may have fallen out, if the retainer cracked beyond a certain the point?

zeroptzero

yeah the rocker arm was an unfortunate victim in this one, the valve dropped into the cylinder for some reason.

I don't think an upshift will cause enough revs to cause float - 3rd gear to 4th gear shift by the OP's report.

postman

Based on his description I'd chalk it up to a faulty rocker arm. Sometimes shit happens. Constant high rpms rarely cause an issue on these engines, and the pcm would have prevented an over rev at that time.

thomsbrain

I'm no engine specialist so don't take this as advice, but it would be interesting to see how well the car could run with just a replaced rocker arm and valves, while leaving the head and piston as-is.

APoner

It wont.... no compression. The valve would never seat. Not to mention the scores on the wall will make the engine smoke immediately and then ultimately fail when the ring lands and rings fail.