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Was this caused by the Money Shift or


Mellow Mike
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here's the results of our M50 "money shift" at Watkins Glen.  A 3rd to 2nd shift at about 7200rpm on the front straight.  we have it on video.  it happened in a blink of an eye.  It took awhile to shake all the bits and pieces out of the exhaust  :D

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Depends on how long the engine was spinning way too fast and floating valves.  All it takes is a kiss between valve and piston to bend a valve head, which can quickly result in a broken valve and then hole in the piston form the valve bouncing around if revs are kept up.  Very short over-rev, and likely only 1 valve was hit hard enough, or enough times, to bend it enough to break it off.   I wouldn't be surprised if all the other exhaust valves are slightly bent.

I had a driver mis-shift a M-50; bent every single exhaust valve.  None of them broke, but there were new indentations in all the pistons.

 

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17 hours ago, Mellow Mike said:

This is the # 6 piston, 1 exhaust valve is destroyed .  BMW M50 engine.  Driver says "I was on the straight-away minding my own business and the engine stopped ".  Tach said 8000 rpm. 

Maybe this was just a tired old engine.

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Your driver lied

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Maybe there was a slight delay between the money shift that bent the valve, and when the valve head broke off and started decorating the piston.  Over-revved it on the back straight, drove three or four corners (long enough to disassociate the two events), it blows on the front straight?

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5 hours ago, NigelStu said:

Depends on how long the engine was spinning way too fast and floating valves.  All it takes is a kiss between valve and piston to bend a valve head, which can quickly result in a broken valve and then hole in the piston form the valve bouncing around if revs are kept up.  Very short over-rev, and likely only 1 valve was hit hard enough, or enough times, to bend it enough to break it off.   I wouldn't be surprised if all the other exhaust valves are slightly bent.

I had a driver mis-shift a M-50; bent every single exhaust valve.  None of them broke, but there were new indentations in all the pistons.

 

 

Was that MIS 2013?

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8 hours ago, NigelStu said:

^It is amazing how much stuff gets sucked back through the intake and deposited into other cylinders.

True, this was my #3 piston in my drag car brand new build custom diamond pistons, broke a valve it went thru #3 sliced the cylinder wall flooding the crank case with water, then sucked it over into #2 chewed that piston and wall up, totally chewed up the head and I was only doing 35-40 @ 2500 rpm. Thank God I wasn't at the stripe WOT @ 120+

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I worked at a shop that ran a sports racer with a 1.5 liter Hayabusa engine.  They had been having some issues with engine harmonics that was causing catastrophic valvetrain failure.  What would happen is that one valve would drop into a cylinder, destroy that cylinder, then debris would bounce over to the next and so on until the whole engine was toast.  They reviewed the data on a couple blow ups and they figured out that the whole process took just over a tenth of a second.  IIRC, they solved that issue by changing how the engine mounted into the frame.  

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8 hours ago, Minneapolis said:

It could look like that if the timing belt slipped or broke at above 5000rpm.  All the valves would start to smack pistons, was the timing belt in the proper position when you opened it up.

All BMW engines except the M20 use timing chains...they very rarely break on their own.  

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On 8/9/2017 at 6:38 AM, TiredBirds said:

True, this was my #3 piston in my drag car brand new build custom diamond pistons, broke a valve it went thru #3 sliced the cylinder wall flooding the crank case with water, then sucked it over into #2 chewed that piston and wall up, totally chewed up the head and I was only doing 35-40 @ 2500 rpm. Thank God I wasn't at the stripe WOT @ 120+

6231212-001.jpg

Nice slugs.

 

Well, they were nice once...

 

That sucks.

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our issue was definitely a money shift.  we have it on video.  he was at redline in third gear halfway down the front straight and in his attempt to shift to 4th he ended up hitting 2nd.  The engine over rev'd and immediately died.  I'd post the video but the drive feels so bad about it I promised him I wouldn't share it with anyone.  he coasted the car to pit out where he pulled off the track.  i assume he was riding the clutch and coasting.

 

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