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ozzo
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Joined: November 14, 2014
Posts: 201
Location: italy
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 Posted: Sat Feb 24, 2018 5:18 am Post subject: broken valve tell me your opinion of reason |
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I was driving... heard toc toc... stopped pulled over and got it at home
today I opened....
I find a broken valve stem...
hear were bougth new 40.000km ago
All HVX hoover mods done
Full flow, oil filter and valves checked every 5000kkm maximum
Broken exhaust of cylinder 4.
No apparently loose power before failure and when adjusting valve newer notice big change to recover
Please see all the picture here...
Any mistake or it seems a defect valve?
Rod seems ok e rod bearing is visually perfect
https://www.blogger.com/blogger.g?blogID=921236914...c=postname |
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UK Luke 72
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Joined: September 07, 2011
Posts: 2867
Location: Little Britain
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ozzo
Samba Member
Joined: November 14, 2014
Posts: 201
Location: italy
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| Posted: Sat Feb 24, 2018 6:46 am Post subject: Re: broken valve tell me your opinion of reason |
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Valve geometry done correctly, oil pressure and temperature correct. The cut in the stem anyhow is below the friction zone to valve guide.
I do not notice any striction or diameter reduction in the broken spot.
Engine in on a bus spinning 3000rpm 80% of the time. Never gone above 4000 rpm. Fully balanced. Head chamber cced..
So i would like to know if it is a defect of the valve or if there is a mechanical mistake..... because or i buy one identical head or i will change brand....head... or whatever.. |
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williamM
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Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Sat Feb 24, 2018 7:53 am Post subject: Re: broken valve tell me your opinion of reason |
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It's possiable to "nick" the valve stem when resurfacing the valve face- that would give the valve a starting place to fail.
You can also get a poorly made valve- older valves were made in several layers of stelite faces, stainless or steel stems. so could have a failure there- not going to mention sodium filled valves there was another source of catastrophic failure there too. A stuck valve can be hit by the piston and bent - the effort to straighten i in the subsequent closing of the valve can cause failures.
Some are just mysteries and we move on.
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ozzo
Samba Member
Joined: November 14, 2014
Posts: 201
Location: italy
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| Posted: Sat Feb 24, 2018 8:32 am Post subject: Re: broken valve tell me your opinion of reason |
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Valve never resurfaced or anything... the point is...
1) should i ask for warranty as it is a clear defect
2) should i keepthe save head and just buy another same to have them pair as it is a builder/ user failure
3) move to another brand of head as this failure indicate bigger manufacturing issue
Thx |
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williamM
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Joined: August 07, 2008
Posts: 4333
Location: southwest Arizona
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| Posted: Sat Feb 24, 2018 8:38 am Post subject: Re: broken valve tell me your opinion of reason |
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All of the above- if you have the energy. According to kombi crew- they ended up having to build their own motor as the quality of the work was so poor,
You might think of that option.
How old is the motor and mileage? Have you talked to the builder yet? Pics?
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opinion untempered by fact is ignorance.
Don't step in any! |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sat Feb 24, 2018 8:51 am Post subject: Re: broken valve tell me your opinion of reason |
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What brand of valves?
A lot....not all.....but a lot of valves are two piece. The head is spin/friction oe induction welded to the stem. Still others have a one piece head and stem and have the hardened tip induction welded on.
While its rare to have a weld fail.....when compared to how many valves are made.....but its not uncommon either.
Ray |
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vwracerdave
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Joined: November 11, 2004
Posts: 15303
Location: Deep in the 405
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| Posted: Sat Feb 24, 2018 8:57 am Post subject: Re: broken valve tell me your opinion of reason |
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Anything with 40,000 KM can wear out and break. Not saying it is normal but after 40,000 KM the part was not defective. Exhaust valves do break over time because the extreme head from the exhaust causes the metal to fatigue.
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jpaull
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Joined: February 22, 2005
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Location: Paradise, Ca
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| Posted: Sat Feb 24, 2018 10:29 am Post subject: Re: broken valve tell me your opinion of reason |
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If its 2 Piece Valve then its the valves fault, or VW. Its a stupid design.
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sat Feb 24, 2018 11:12 am Post subject: Re: broken valve tell me your opinion of reason |
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| jpaull wrote: |
| If its 2 Piece Valve then its the valves fault, or VW. Its a stupid design. |
Why?...and why is it a stupid design?.....the vast majority of valves produced over the last half century or more....are two piece valves.
Induction and spin welding...are quite a high science. Unless you are running high rpm, racing or forced induction....the vast majority of valves you buy from companies like SI, Ferrea and Manley...are two piece valves.
When you move up into their high end valves for racing...most are one piece and exotic alloy....and usually start at $85 a valve unless its a common valve they stock. I just priced some Ferrea valves Friday.
For a stock or slightly hotter ACVW or virtually any stock-ish "passenger" vehicle....two piece valves are the norm.
Do you have stainless valves with hardened tips? If so...look closely....how do you think that hardened tip got there? The vast majority of the time its a spin or induction welded segment about 0.5" long.
I agree with vwracerdave. If it made it 40k kilometers...about 25k miles....it was not defective...per-se. It may be one of the few in a million that was under strength...who knows. If it had failed in 5k miles or less...when everything was known to be perfect....I would say its defective.
This is why I am asking what brand. A no name brand? A known brand? Look up at the top of the stem with a magnifying glass and look for marks and stampings.
Ray |
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ozzo
Samba Member
Joined: November 14, 2014
Posts: 201
Location: italy
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| Posted: Sat Feb 24, 2018 11:28 am Post subject: Re: broken valve tell me your opinion of reason |
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Ok... so watching just steam and valve seat is not possible to get the most probable reason??
What get me angry is that i built this engine to stay on 3000 rpm to live long.... stock cam... etc... i expected at least 100.000km before having this issue... it never happened with stock heads ..
By the eay i paid the extra $$ for having ss valve installed...
Other way around does it exist an head that in pretty stock motor condition can run 100.000km without catastrophic failure?
I ll share brand after i have an official reply from manufacturer |
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Dale M.
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Joined: April 12, 2006
Posts: 20378
Location: Just a tiny bit west of Yosemite Valley
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| Posted: Sat Feb 24, 2018 12:03 pm Post subject: Re: broken valve tell me your opinion of reason |
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| ozzo wrote: |
Ok... so watching just steam and valve seat is not possible to get the most probable reason??
What get me angry is that i built this engine to stay on 3000 rpm to live long.... stock cam... etc... i expected at least 100.000km before having this issue... it never happened with stock heads ..
By the eay i paid the extra $$ for having ss valve installed...
Other way around does it exist an head that in pretty stock motor condition can run 100.000km without catastrophic failure?
I ll share brand after i have an official reply from manufacturer |
Ever heard the phrase "Shit Happens"....
Dale
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ozzo
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Joined: November 14, 2014
Posts: 201
Location: italy
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| Posted: Sat Feb 24, 2018 12:15 pm Post subject: Re: broken valve tell me your opinion of reason |
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Dale yes but this is my daily driver and i also go many km away with two little girls for holydays.... i did everything i could to make it reliable.... if it will never be better than this i will never take it for holydays anymore and just call it a toy.... and actually i do not want....
So is there a head that will not suffer this or which valves should i get to keep peace of mind? |
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ps2375
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Joined: April 24, 2014
Posts: 2471
Location: Meridian,ID
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| Posted: Sat Feb 24, 2018 12:36 pm Post subject: Re: broken valve tell me your opinion of reason |
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| Is this the first valve you have had this happen to? I've never had it happen, ever on any car. Call it luck, good or bad, but I doubt you'll have it happen again, given how you drive it and build spec. |
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modok
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Joined: October 30, 2009
Posts: 26781
Location: Colorado Springs
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| Posted: Sat Feb 24, 2018 1:27 pm Post subject: Re: broken valve tell me your opinion of reason |
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I cannot access the picture.
Valves usually break because the guide is worn out, or the guide is not aligned with the seat.
The job of a guide.... is to guide the valve back to it's seat, so I would check to see if it was doing it's job. |
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UK Luke 72
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modok
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Joined: October 30, 2009
Posts: 26781
Location: Colorado Springs
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| Posted: Sat Feb 24, 2018 2:11 pm Post subject: Re: broken valve tell me your opinion of reason |
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| Lower shelf, but at least on the shelf. |
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wcfvw69 
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Joined: June 10, 2004
Posts: 13389
Location: Arizona
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| Posted: Sat Feb 24, 2018 2:13 pm Post subject: Re: broken valve tell me your opinion of reason |
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| ozzo wrote: |
Dale yes but this is my daily driver and i also go many km away with two little girls for holydays.... i did everything i could to make it reliable.... if it will never be better than this i will never take it for holydays anymore and just call it a toy.... and actually i do not want....
So is there a head that will not suffer this or which valves should i get to keep peace of mind? |
I've driven air cooled VW's for 35 years and never suffered a broken valve, loose valve seat, etc.. Maybe I'm lucky? IDK, I'm like you in that I do my preventative maintenance religiously too.
In your case, sometimes you just have to consider it bad luck. ALL cars, including news ones break down. I see new cars on tow trucks all the time due to a break down. I wouldn't let this one issue scare you into thinking your VW is unreliable.
Find a really good machine shop to inspect your head to see if they can determine why the valve broke. I'm sure they can. I'd also install the best valves you can buy when you have the heads rebuilt.
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modok
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Joined: October 30, 2009
Posts: 26781
Location: Colorado Springs
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| Posted: Sat Feb 24, 2018 2:23 pm Post subject: Re: broken valve tell me your opinion of reason |
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I'm not worried at all about valves breaking.
Used to be a real problem 60 years ago but these days very rare, as the materials are far better.
I've seen keepers break and valves break at the keeper grooves more often.
You have to screw up bad or be very lucky to break a valve.
The guides in AMC heads wear rapidly and that can cause this. Been that way for a long time. Not all that is "new" is good. |
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raygreenwood
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Joined: November 24, 2008
Posts: 21512
Location: Oklahoma City
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| Posted: Sat Feb 24, 2018 3:18 pm Post subject: Re: broken valve tell me your opinion of reason |
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| modok wrote: |
| Lower shelf, but at least on the shelf. |
Yes.....in general...SI is lower shelf....but I know a few people that like them a lot.
Years back.....for a while....I think Jake Raby was using SI valves in some of his type 4 engines....but also noted....IIRC.....that what he was using was custom and ordered to his specs and in quantity.
Also.....I do not fully get where everyone is noting that stainless valves are the way to go.
Yes.....they can handle heat a little better because stainless in general (not really getting into specific alloys).....has slightly better heat conduction than ferrous steels....and metter malleability to all flow shaping around the valve periphery....and its slightly lighter
That being said.....there are no stainless valves that are internally as hard as some or the better steel valves. The stainless valves depending on alloy can get stretchier.
And....high temp stainless alloys are more complex to control the quality of......and.....just so everyone realizes.....the vast majority of stainless alloys and stock are made in China and have been for some time.
I remember right about 20 years ago....maybe a little more or less......stainless valves were more expensive and most of what was available was made by "the good companies".
Then all of a sudden every build you read about in the mags......snd everything anyone was talking about was pushing stainless valves.....had to be "SS"..and they suddenly got cheap.
You could buy stainless valves from every crappy parts house in the magazines......and 90% of the time....there was no manufacturer recommended.
Good stainless valves are excellent. Cheaply made valves of any material are a risk.
If you paid extra $$.....for stainless valves....there had better be a name attached. Ray |
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