Rocker arm failure on track
 

*Crosspost from Under the hood*

So finally got back out there after an 11 month hiatus and some pretty significant changes to the car. Here are some details of my motor setup

31k miles on the clock
AEM infinity tuned by National Speed in Wilmington
AP2 intake retainer upgrade installed by a competent s2k mechanic (he's done a number of other retainer upgrades around the area for s2000 owners)
Berk headerback
k&n fpk
Amsoil Dominator 10w-30 racing oil
OE filter (always)

Well finally back from VIR and Sunday wasn't the greatest of track days for me. Saturday runs were great and I was loving the tuned power output. The car felt great. Got out there this morning and warmed the car on grid, did our slow paced warm up lap and then started our hot lap. We weren't half way through when the engine let go. I completed my 4th to 5th upshift and was north of 7500rpm when it sputtered and then shut down. I was towed back to paddock and took the valve cover off to find pieces of the rocker arm for cylinder 2 hanging out in the head, and with the car in neutral I am unable to turn the motor more than 90 degrees. I also cant get the spark plug out to bore scope it. Anyway, just wanted to add myself to the list of rocker arm failures. I'm sorry to see I'm not the only one:

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Now the only question is to rebuild or do a K swap.

Any downshift over revs?

That is interesting, you broke the rocker but didn't drop a valve?

No sir, not while I've owned it. Intake valves were recently upgraded to AP2, but this was exhaust side.

Correct. Really weird huh?! The only thing I can think of is that the piston contacted the valve while the cam lobe still was pushing on the rocker, and the rocker was the point of least resistance. Looking at the broken piece, it seems it crack from the bottom up.

Do you have better pictures of just the cracked arm...where it cracked? If I understand the picture of one side, it cracked around the roller and that part of the crack area had some corrosion. Is that correct? If so, it is may just be fatigue in a damaged part. A lubrication problem could have made it worse.

Was it a clean break into 2 pieces or was their shrapnel that flowed into the oil system?

Yeah I can take those tonight. It was a really clean break actually. The other half is still on the roller guide (if that's what you call them). I am unaware of any corrosion. The motor was and is really clean. Fatigue is likely, but I'm more suspect of a timing issue allowing a slight bit of contact between the piston and valve, thus shoving the valve stem into the head of the rocker. The arm just happened to be the weakest part. Anyway, that's my theory right now until we get the head off and inspect the piston.

Got the spark plug out last night with a decent amount of effort. I'm confident the head is trashed.

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This makes me wonder if having cams such as Toda VTEC killers would have prevented this. Interesting point.

Recently did the same on mine. Never over revved it. had it since 5k.