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Engine Blew: Rocker arm and Valve Causes?

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Engine Blew: Rocker arm and Valve Causes?

 
Old 08-05-2018, 04:14 PM
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Default Engine Blew: Rocker arm and Valve Causes?

UPDATE: The likely caused was identified. I put in a new engine (unfortunately it was an ap1 motor instead) and I tried to prime the fuel pump but it didn't. It seems the old oem fuel pump died. I put in a new fuel pump and worked no problem. My theory is the engine wasn't getting enough fuel, which burnt my exhaust valves in Cyl 3. The EXHAUST valves subsequently weakened from getting too hot, and snapped off at the stem. With the valves broken off and getting chewed by the piston, the intake valves open up and with the interference of the valves, the push up against the intake valves, which push against the rocker arm and break them off. Moral of the story? Replace more of the car's components as preventative maintenance if you are tracking your car.

Hi all. Let me start by saying this community is awesome. The resources have been super helpful with me getting as far as I have. It is ironic that I had an engine fire a few weeks ago (post) at the local track here in MN and then this Friday I blew up the engine. When it rains, it pours right?

Some quick details of the background on the car from when I bought to today:
- Bought flood damaged salvaged 2006 Ap2 from AZ auction last year with 136K miles.
- Water was present in oil. I flushed it 3 times to get it out.
- Compression was within spec and ran like a champ. Though, cylinder 1 was barely in spec.
- Valve lash was over tight and likely caused scorched cam lobes (previous owner). I adjusted them within spec.
- Over the winter I took it all part to build a dedicated track car. (seat, harness, rollbar, coilovers, poly bushings, new accessories, wheel bearings, extended studs, moroso oil baffle, RAIN H8R VC mod)
- The car has seen about 10 track days since last year with many oil changes. I did a blackstone sample and I was a little high with aluminum, iron, and silicon (wtf?). Engine now has 155k miles on it.
- Had fresh oil in engine (5w30 mobil 1) though, level was a little high.

So, last Friday, first lap of the day I spun out. I clutched in so the engine didn't die. Got back on the track and pitted to make sure nothing was damaged. Everything seemed ok. So, I had time for one lap. Turn 3 is a 1st gear corner and immediately up shifting to 2nd, died. No boom, or smoke or fire - just a subtle engine dying with a weird whir to it. Crap.

Got towed to the paddock. Nothing can be seen. Tried to start the engine, click. No turn over. Tried to hand crank it. Motor was stuck and would not move. Towed it home and dropped the engine oil. metal flecks and bits. Super crap. Started dismantling the vc and throttle body and found surprises. Looks like it literally ate an intake valve and a rocker arm on cylinder 3. Then, shot the valve bits back in the intake manifold.




The goal of this post is to figure out what could have caused this so I can prevent this from happening again as a weigh my options for Engine 2.0. Any advice from those with engine building/blowing up experience would be most helpful. I am also seeking a local s2000 engine builder local to MN, so if you know someone I'd love to get connected. I will be pulling the head this coming weekend to inspect the true damage.

My options in priority for a new engine are as follows:

1) Used engine swap with something less than 50k miles. The problem with this is engines with these miles are $$$. Only finding ones in Japan for $5.5k but it comes with tranny.
2) Buy a salvaged s2000 and pull the motor and part it out. Risky if it is not a run and drive motor. Would hire a remote mechanic to inspect. I can get a low mileage s2000 that was in a wreck for about $3-4k.
3) Rebuild. Unlikely since the head and cylinder are likely toast.
4) K-swap. The swap is possible with kits but swapping it the first time is nearly the same cost as used F22c (adapter plate for tranny and manifold, custom ex manifold, coolant reroute plates, custom clutch, motor mounts) + donor motor and wire harness.

Last edited by weenrock; 04-15-2019 at 07:13 AM.
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Old 08-05-2018, 04:52 PM
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One likely cause could be a cracked retainer which allowed the valve to drop, then it all went south from there. Hard to diagnose anything over the internet but that would be my best guess.
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Old 08-06-2018, 05:13 AM
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A broken retainer even after it reaches its extreme state and breaks the valve tip off will not break a rocker arm. There is something else going on there...
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Old 08-06-2018, 06:43 AM
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Originally Posted by Billman250 View Post
A broken retainer even after it reaches its extreme state and breaks the valve tip off will not break a rocker arm. There is something else going on there...
My thought exactly. It is a 2006 so it has the better retainers. I haven't seen other damage anywhere else. Just the one valve and rocker.
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Old 08-06-2018, 06:51 AM
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Could this happen from over-rev or TCT failure?

Thanks!
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Old 08-06-2018, 07:54 AM
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Originally Posted by windhund116 View Post
Could this happen from over-rev or TCT failure?

Thanks!
When I pull the head, I can inspect the TCT. I didn't overrev it when it failed. I reviewed the onboard footage and saw that I shifted from 1st to 2nd just below redline.
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Old 08-06-2018, 08:52 AM
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Did it have stock ecu, no aftermarket VTEC adjustments?
Similar issue also happened on up shift https://www.s2ki.com/forums/s2000-un...r-arm-1144455/
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Old 08-06-2018, 09:00 AM
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100% stock motor and ecu. No adjustment to vtec or cams.
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Old 08-06-2018, 10:22 AM
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Originally Posted by Billman250 View Post
A broken retainer even after it reaches its extreme state and breaks the valve tip off will not break a rocker arm. There is something else going on there...
not trying to be "that guy" but I have two scrap f20 cylinder heads at my shop right now that both dropped an intake valve and broke the rocker...
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Old 08-06-2018, 10:26 AM
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Originally Posted by Charper732 View Post
not trying to be "that guy" but I have two scrap f20 cylinder heads at my shop right now that both dropped an intake valve and broke the rocker...
There isn't a whole lot of difference from my f22 head other than the retainers, right?
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