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Totally destroyed our E30 motor


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By the way one of the guys set the head down on the valves after taking it off, I'd assume a valve got bent during assembly.  Give it a few thousand RPM for a few minutes with a bent valve stem, valve head fatigues off, and boom.  Once the cam is in the head (or even the first rocker is installed), the head should never be placed chambers down anywhere. Those valves do not tolerate any side load, even just supporting the weight of the head is enough to bend them.

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10 minutes ago, Hi_Im_Will said:

By the way one of the guys set the head down on the valves after taking it off, I'd assume a valve got bent during assembly.  Give it a few thousand RPM for a few minutes with a bent valve stem, valve head fatigues off, and boom.  Once the cam is in the head (or even the first rocker is installed), the head should never be placed chambers down anywhere. Those valves do not tolerate any side load, even just supporting the weight of the head is enough to bend them.

I would have to say Hi Im Will is spot on . We run into this with the VW 1.8 T head and pumped up lifters after a Tbelt  breaks or and VW lifters not de bled when resembled.

Bob Mann

www.DRVOLKS.com

bobtec@comcast.net

drvolkslogo.jpgtdtuninglogo.jpg

 

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1 hour ago, NigelStu said:

How are the rocker arms?

 

And rod caps?

 

I was thinking this until.....

 

56 minutes ago, Hi_Im_Will said:

By the way one of the guys set the head down on the valves after taking it off, I'd assume a valve got bent during assembly.  Give it a few thousand RPM for a few minutes with a bent valve stem, valve head fatigues off, and boom.  Once the cam is in the head (or even the first rocker is installed), the head should never be placed chambers down anywhere. Those valves do not tolerate any side load, even just supporting the weight of the head is enough to bend them.

 

I saw the video and Will commented about this.  I would assume the same thing as Will is stating....no bueno.  

59 minutes ago, JDChristianson said:

Looks like a case of intergranual stress metal comesapartous.  Followed by wonderingbitsofstuffitis.   In less scientific terms it broke

 

 

You just like to say things broke.....

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Reviewing the video again, rod exposed end looks to be in about the correct height, and is facing about where you'd expect a slightly bent rod to be facing.  The valve would have done all the damage to the piston.

 

So, step 1 - valve broke.  Step 2 - destruction.  Step 3 - profit.....

 

 

Question would be WHY did the valve break.  Doesn't take long for even a very minor bend in the stem to break the head off: think of how many times the valve leaves and returns to the seat in 1 minute when you are running the engine at 4-6K RPM....   With uneven pressure, it doesn't take long to break one.  

 

I would expect an assembly issue or possibly a part failure not related to assembly.

  • As Will stated, based on how the head was set down, there is potential head was set down in the same manner during assembly and pre-bent a valve.  
  • Valve was already bent from something else before install
  • Rocker clearance too tight, allowed valve to just barely contact piston (doesn't take much)
  • valve keeper not installed correctly (probably not, otherwise failure would have occured sooner)
  • towers/head shaved and or CAM out of spec on lift and clearances not checked
  • rocker broken, stuck valve open (hard to tell in video, but it doesn't look like any of the rockers are broken/out of place)
  • valve seat not installed fully, came loose or was not pressed in far enough which makes starting point of valve further in the cylinder
  • Spark plug electrode or some other foreign object got in there, valve closed on it.
  • timing was off, belt jumping a tooth (not likely, would expect more carnage)

 

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As another option, M20 engines are getting old, which means most of the M20 heads are starting to see wear in the camshaft journals.  Being a straight 6, those camshafts are nice and long and can get into some nasty resonance vibrations at high RPMs if there's play in some of the journals.  This can cause a failure of a spring retainer and just drop the whole valve into the cylinder.

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Not sure what caused your damage, but we had a similar Problem at an event last year. Parked the car Saturday, it was running fine, got in hit the button Sunday morning and it sounded like somebody dropped a box of rocks on the crank case.  hope you all get it fixed up soon. We are about to put ours back together.

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  • 1 month later...
On 1/26/2017 at 11:45 AM, Hi_Im_Will said:

By the way one of the guys set the head down on the valves after taking it off, I'd assume a valve got bent during assembly.  Give it a few thousand RPM for a few minutes with a bent valve stem, valve head fatigues off, and boom.  Once the cam is in the head (or even the first rocker is installed), the head should never be placed chambers down anywhere. Those valves do not tolerate any side load, even just supporting the weight of the head is enough to bend them.

 

We set it down on the valves after we took it off because it was obvious the whole thing was garbage at that point. We were very careful not to do this before assembling the motor.  That said, I don't know how the head was handled before it got to me and I suspect it may not have received the treatment.  

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On 1/26/2017 at 1:34 PM, NigelStu said:

Reviewing the video again, rod exposed end looks to be in about the correct height, and is facing about where you'd expect a slightly bent rod to be facing.  The valve would have done all the damage to the piston.

 

So, step 1 - valve broke.  Step 2 - destruction.  Step 3 - profit.....

 

 

Question would be WHY did the valve break.  Doesn't take long for even a very minor bend in the stem to break the head off: think of how many times the valve leaves and returns to the seat in 1 minute when you are running the engine at 4-6K RPM....   With uneven pressure, it doesn't take long to break one.  

 

I would expect an assembly issue or possibly a part failure not related to assembly.

  • As Will stated, based on how the head was set down, there is potential head was set down in the same manner during assembly and pre-bent a valve.  
  • Valve was already bent from something else before install
  • Rocker clearance too tight, allowed valve to just barely contact piston (doesn't take much)
  • valve keeper not installed correctly (probably not, otherwise failure would have occured sooner)
  • towers/head shaved and or CAM out of spec on lift and clearances not checked
  • rocker broken, stuck valve open (hard to tell in video, but it doesn't look like any of the rockers are broken/out of place)
  • valve seat not installed fully, came loose or was not pressed in far enough which makes starting point of valve further in the cylinder
  • Spark plug electrode or some other foreign object got in there, valve closed on it.
  • timing was off, belt jumping a tooth (not likely, would expect more carnage)

 

These are all excellent theories. The leading one at this point is that that retaining clip that holds the valve in place either popped off, failed or was never installed. I noticed it was missing (or shredded with other parts) when I pulled the head off. I wish I knew what happened, but I do know we won't be using the machine shop that put it together ever again.

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