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RB25 NEO Piston eats Valve (carnage)

ArcticSIlver
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ArcticSIlver Rookie

ArcticSIlver

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Was at the track a couple days ago when my motor made horrible noises at rev limiter. Pulled the motor out and took the head off to inspect. One exhaust valve broke entirely and bent all the rest in the same cylinder (#1) for obvious reasons. I am very unsure what happened, I suspect valve float? Rev limiter is set to 7800. 10 events on a fresh rebuild, standard engine besides arp head studs, arp rod bolts, ACL race bearings, and cometic head gasket. It was running fantastic and rock solid all year. The valve spring, keeper, and retainer were all in perfect shape. I find it curious though that the valve stem was not bent, almost like it did not contact the piston at the time of breaking. Timing was dead on, and car was dyno tuned by a very good tuner at 412hp. Any ideas? would like to prevent this on the new motor.

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Leroy Peterson Grand Master

Leroy Peterson

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Are you planning to run aftermarket springs and retainers on the new motor?

Looks like a pretty clean breakage... Had the motor been pulled down previously? Any idea if it had a hard life before you had it? Otherwise I got no idea

ArcticSIlver Rookie

ArcticSIlver

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Ill run aftermarket valve springs if I need to, I was just planning to slap all my goodies on the new motor and get a tune and drive it. It had only 10 events on a legit rebuilt. Maybe 500 miles on it. It was on 17psi boost and at the moment I had been on limiter for 3 seconds maybe? However this is a drift car and I have been giving it bloody hell ever since it's been running and tuned.

Dobz Experienced

Dobz

Posted
Posted

It would be hard to pin point exactly what went wrong. Being an exhaust valve it has somehow stayed open when it should have been retreating back to its seat. Possibly bouncing badly off the cam when on the limiter with the engine abruptly cutting power whilst manifold back pressure is slowing down the valve closing.
A heavier valve spring would help ensure the valve will travel back to the valve seat when it should.

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