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The exact cause. I would take the 2 old parts to a Metallurgist and find if it was a shock breakage or wear
 
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Discussion Starter · #62 ·
The exact cause. I would take the 2 old parts to a Metallurgist and find if it was a shock breakage or wear
Owner has the parts, out of our hands. At the end of the day, does it matter? It broke, it's extremely rare (perhaps first ever?), and it's now fixed. Why dump more money into something that isn't a problem?
 

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Owner has the parts, out of our hands. At the end of the day, does it matter? It broke, it's extremely rare (perhaps first ever?), and it's now fixed. Why dump more money into something that isn't a problem?
"The Internet" would be interested to know.

Do you know if the owner get all their ESC premium refunded? This sort of thing doesn't make McLaren look good. I'm really pleased that the owner had McMedics to call on.
 
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Discussion Starter · #64 ·
"The Internet" would be interested to know.

Do you know if the owner get all their ESC premium refunded? This sort of thing doesn't make McLaren look good. I'm really pleased that the owner had McMedics to call on.
It's a freak thing, if people talked about the Lamborghini and Ferrari failures it wouldn't look good for them either. Mentioning anything short of perfection looks bad in the eyes of the internet. As far as the premium being refunded, I don't know, I only know that policy got cancelled.
 

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Owner has the parts, out of our hands. At the end of the day, does it matter? It broke, it's extremely rare (perhaps first ever?), and it's now fixed. Why dump more money into something that isn't a problem?
Of course it matters this is how the rest of us can learn to avoid it, fyi this isnt the first time it has happened either, have a brief search and you will see.
 
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Discussion Starter · #66 ·
Of course it matters this is how the rest of us can learn to avoid it, fyi this isnt the first time it has happened either, have a brief search and you will see.
I did a search and came up empty. I believe the arm broke because the cast was faulty, to prevent this you never start the car ever again.
 
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I did a search and came up empty. I believe the arm broke because the cast was faulty, to prevent this you never start the car ever again.
Ok let me help with that.


Haha, funny Sean, to me it looks like wear getting to the point of brittle which would make sense considering the exact point of failure on the rocker.
 
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Discussion Starter · #68 ·
Ok let me help with that.


Haha, funny Sean, to me it looks like wear getting to the point of brittle which would make sense considering the exact point of failure on the rocker.
I think you're misunderstanding what the issue was in this case. What you cited was worn rockers, and in one of the links showed a broken one that was severely worn. What we saw in this engine was not wear. All of them looked fine, and the lobe to the broken one had less wear than the rest of the lobes. Wear was not an issue on any of them, it simply broke.
 

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I think you're misunderstanding what the issue was in this case. What you cited was worn rockers, and in one of the links showed a broken one that was severely worn. What we saw in this engine was not wear. All of them looked fine, and the lobe to the broken one had less wear than the rest of the lobes. Wear was not an issue on any of them, it simply broke.
:(
 

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Something has popped into my mind about this actually, so the s54 that is used in the e46 m3 has a very similar valve train to the mclarens, the valve clearances needed adjusting with shims, for some reason on the mclaren this isnt needed. Could it be that the shim was warn so much the distance between the rocker and shim could have increased so that the follower was taking more of a beating?

If someone knows about the no need for shim changes to adjust valve clearances on the M8T engine that would be good.
 

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Ok but that doesnt mean it shouldnt be done. What i wana know is what happens when they wear then
 
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Discussion Starter · #73 ·
Ok but that doesnt mean it shouldnt be done. What i wana know is what happens when they wear then
They probably don't wear the same. I'm guessing that's the case based on BMW's history of valve guide seal issues.
 

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which brings up the question of how is the valve lash taken up on the 838 engines?
Exactly, also my S54 engine was driven HARD and i mean HARD, 8k rpms daily from 1st gear. Zero valve train issues with 120k miles. to be fair, the shims are probably 3x the thickness of the S54 engine, even after many miles.... So it might not even be an issue and those shims are HARD like you would never believe
 

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Exactly, also my S54 engine was driven HARD and i mean HARD, 8k rpms daily from 1st gear. Zero valve train issues with 120k miles. to be fair, the shims are probably 3x the thickness of the S54 engine, even after many miles.... So it might not even be an issue and those shims are HARD like you would never believe
you're saying mac uses shims to adjust lash? if so,where are they located? didn't see anything in maintenance list relating to valve adjustment periods afaik.
lash change in most engines doesn't come from valve train wear, it comes from valves and/or seat recessing,stem elongating etc..
 

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Skip to 29.50 of the original video. I think those will be the four shims from the removed rocker assembly.

32:40 you can see that it sits between the valve stem and the rocker arm.

I'm assuming McLaren will have some specs on clearances when cold for those parts and possibly have a few sizes available in their parts catalogue.
 
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Skip to 29.50 of the original video. I think those will be the four shims from the removed rocker assembly.

32:40 you can see that it sits between the valve stem and the rocker arm.

I'm assuming McLaren will have some specs on clearances when cold for those parts and possibly have a few sizes available in their parts catalogue.
will look at video. thanks
 

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Sean and I are at it AGAIN.... 😎



Kevin P
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"The Internet" would be interested to know.

Do you know if the owner get all their ESC premium refunded? This sort of thing doesn't make McLaren look good. I'm really pleased that the owner had McMedics to call on.
I canceled the 3rd party policy (not McL warranty) and got the balance refunded. I have the parts but don't have a metallurgist on speed dial. I've been meaning to write a review but I've been too busy enjoying the car daily. I'll get to it soon enough, for "the Internet's sake" :)

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