Topic: E30 carnage at Laguna

Shattered a piston in our E30 at a race a couple weeks back. I've never seen such carnage! The motor was an hour old. Anyone have an idea what might have caused this? No over rev, no overheating. Fresh build, but I suspect the head.

https://youtu.be/29nX6O-IzYo

Shattered Piston

Racing YouTube channel: https://www.youtube.com/c/revmatchtv

Re: E30 carnage at Laguna

From the look of it, that valve hit the piston and broke it off.  It wedged onto the side of the cylinder and got caught between the piston and head and the piston lost that battle. 

So the question is - how did the piston come in contact with the valve?  Did you happen to find any extraneous parts?  I'm guessing that something found its way into the intake tract, ended up lodging that valve open where it contacted the piston where it bent and/or broke. 

Did you happen to check the cam timing before you took the head off?  The timing belt could have slipped but that usually leads to every valve getting bent not just one.

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Re: E30 carnage at Laguna

I always thought these things were chicken/egg situations between piston/valve.  Probably the biggest clue is how new the engine was but without knowing what was replaced, it's hard to say.  I would think that FOD would have blown it up quicker than an hour.  I'm wondering if a keeper didn't get installed correctly.  Also wouldn't rule out incorrect ring gap and piston bits took out the valve rather than the valve taking out the piston.  If the ring gap was too tight, I can't imagine that happened on just one piston so perhaps the other piston rings can provide a clue.

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4 (edited by billybobster 2017-02-02 10:47 PM)

Re: E30 carnage at Laguna

Don't know if folks have seen their video showing the head - https://www.youtube.com/watch?v=aUBPPQxHa6M

I'm an engine internals newb, but it looks like there was valve/piston contact on two of the other cylinders (valve seat fragment - valve shaped ding on piston), apart from the one that went boom. Timing belt "issues" were my first thought.

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