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Have you had a valve failure? Please fill out the form below (hit quote on post 2) if you have!
Yes 12%  12%  [ 6 ]
No 35%  35%  [ 17 ]
Not Yet (But I'm worried) 37%  37%  [ 18 ]
Not Yet (Not worried) 16%  16%  [ 8 ]
Total votes : 49
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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Mon May 29, 2017 2:10 pm 
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Joined: Tue Sep 27, 2016 6:11 pm
Posts: 10
Location: Harlingen, TX
CRD Year: 2005 Limited
Mileage at failure: 113K
Mileage with functional EGR: 102K
Method of EGR delete (elbow, GDE, SEGR, died and you didn't fix): GDE and Elbow Kit
Most common driving (city/highway/mountains/etc): Mixed
Do you have an Exhaust Temp gauge: No
Pre or post turbo:
If so, most recent average running temp you remember:
Any issues with overheating in the recent history before your failure?: No, thermostat was actually failed open and running cool. Valve broke a few months after replacing thermostat. Never once got close to overheating.
ARP studs? No
Replacement rockers? Yes, at 102k
Time / mileage between engine work and valve failure? 4 years and 11k miles.
Which cylinder failed? 2
How many valves, and which ones broke? Not sure.
Did the stem break, and was it where the chrome met the black, in the middle of the black, or at the valve "coin" itself?
Do you have any pictures, and can you link / post them here please?
Can you also post a picture / report what the cylinder head stamping was?

I'm not 100% sure, but I believe my 2005 CRD has a broken valve in cylinder #2. I was cruising down the highway and without warning the engine started running rough, lost power, and smoke was pouring out of the exhaust. Check engine light came on and read cylinder 2 misfire. I tried removing the injectors so I could do a compression test but the #2 injector would not budge. I found a mechanic who has experience working on these jeeps and has all of the tools, including injector pullers. However, even the pullers could not remove the injector. He said that he has seen this a handful of times on these vehicles and that every time it was due to a broken valve causing the injector tip to break/mushroom, preventing it from coming out. So the only way to verify would be to pull the cylinder head. Unfortunately, I just don't have time or money to get it fixed so if anyone is interested in purchasing this vehicle as is please pm me. The rest of the jeep is in very good shape and would make a good project for those on this forum that have the ability and time to work on it. The turbo, timing belt, rockers, oil cooler, and thermostat have all been replaced in the last 4 years. Thanks.

_________________
2005 Liberty CRD Limited
Green Diesel full torque tune, timing belt, rocker arms, turbo replaced at 102,000, 5v glow plug conversion
113,000 miles as of 2/6/2017


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Mon Jun 12, 2017 2:51 am 
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Joined: Sat Jul 10, 2010 7:38 pm
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Location: The Dalles, OR.
OOh. I wanted to go to the CSM. Never happened though. I have a though on the defective valves though. If they are failing, replace them with better ones... Factory valves are generally not picked for longevity unless you are Cummins, Cat or Lister...

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GDE FT Ecotune, EHM, Weeks kit stage 1 & 2, Carter 4600 lift pump, Upgraded tranny, Fishing boat hauler!


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Mon Jun 12, 2017 7:29 am 
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DieselJeepLuvr wrote:
OOh. I wanted to go to the CSM. Never happened though. I have a though on the defective valves though. If they are failing, replace them with better ones... Factory valves are generally not picked for longevity unless you are Cummins, Cat or Lister...

So who can supply a better valve? That would be a great and worthy upgrade, and that question has been asked on here before, but never an answer found that I recall... :roll:

_________________
05 Jeep Liberty CRD Limited :JEEPIN:
Blk Brush Guard/Hella's/LED's
Ironman Springs/Bilstein's
Yeti Stg4 MaxTune
Weeks ElbowKit/Battery Tray
NO FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pump
2mic.Sec.Fuel Filter
Flowmaster/NOcat
V6 Airbox
GM11 blade fan/Hayden HD clutch
Ironrock Trilink
98 Dodge Cummins, 5"exh. Viair,K&N


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Jun 15, 2017 2:33 pm 
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Joined: Tue Dec 16, 2014 9:33 pm
Posts: 244
Location: Jackson,TN
Phx Flyer on page one of this thread stated that he had used a company in england to make custom valves. I assume he is an aviator or AP who deals with the air cooled Lycoming (since Lycoming was mentioned) aircraft engines that have normal head temps about 450 F IIRC no telling what cylinder etc temp is but I assume they are not diesels at least the ones I am familiar with in light aircraft such as a cessna 150 and others. I presumed modified aircraft racing engines would need high quality custom valves.


Maybe Phx Flyer can inform us what the name of the company is. I am sure he intended to contact them after the metallurgy data is reported. Wonder if he lives in one of the aircraft fly in communities in Arizona. Talk about fanatics on maintenance they have to be. They also can't do many modifications due to FAA regulations but I assume racers can.

_________________
05 Blu LIM, OME GDE Tbo, wk II,, 255/75/17 BFG Mud, KC Lights, bull bar, 161K H TC
05 Blu Lim, Dayton, GDE HT, 255/75/18 Dueler AT, 188K , H TC
06 Bla Lim, GDE Eco, Destination AT 245/75/17, 151K, H TC
06 D Khaki Lim 98K wkII Eur TC
01 F350 7.3L Du
CRDS: Fumoto, Kennedy Lift , Fan Shroud mod, fuel head, SAMCOS,self TB, 2 Mic filt, Hayden


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Jun 15, 2017 2:59 pm 
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Joined: Tue Dec 16, 2014 9:33 pm
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Location: Jackson,TN
I do find it interesting that the failures on two were 200 miles one 700 miles and one 4,000 miles after work but of course correlation and causation are not the same. Otherwise one could conclude that ARP stud replacement or replacing rockers (BTW were they replaced with the new version?) or adding the weeks kit were causes.

The one valve failure under the previously broken rocker makes sense on one level maybe the rocker didn't really do its job.

I do personally wonder if a speciific combination of rocker and arp studs could even contribute. I am fixing to either replace just ARP or ARP and head gasket depending on what i find on teardown. I was planning on replacing rockers also with either scenario. Is th e design so tight that further compression of the head gasket with ARP s and new rockers that are not worn could essentially reduce clearance enough to be out of tolerance? I would say no, since the valves also have wear which would increase it some compared to new engine. Are the new rockers actually oiling better? If the ARP s and rockers were being replaced prophylactically I can see this as a very remote possibility. If they are being replaced after broken rockers I would personally expect sometimes the valves were unknowingly stressed or damaged. Maybe I shouldn't fix the head gasket leak and just run it till it failed catastrophically!!!! LOL! :ROTFL: I am afraid to touch it and spend all the time and money then have it fail in 200 miles! Thankfully I have overcome the fear and am proceeding with the repair. If a brand new head did it I will take my chances.

I will report after 1,000 miles if I make it that far!

_________________
05 Blu LIM, OME GDE Tbo, wk II,, 255/75/17 BFG Mud, KC Lights, bull bar, 161K H TC
05 Blu Lim, Dayton, GDE HT, 255/75/18 Dueler AT, 188K , H TC
06 Bla Lim, GDE Eco, Destination AT 245/75/17, 151K, H TC
06 D Khaki Lim 98K wkII Eur TC
01 F350 7.3L Du
CRDS: Fumoto, Kennedy Lift , Fan Shroud mod, fuel head, SAMCOS,self TB, 2 Mic filt, Hayden


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Sat Jul 22, 2017 3:33 pm 
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Joined: Fri Mar 20, 2015 2:11 pm
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Location: markham, ontario
ok back on this thread again ,, so my understanding is that exhaust valves are made in VM factory in Istanbul Turkey , i think for the people that experienced these RARE failures (broken valve) , I think it is worth contacting the manufacturer and sending them faulty valves for inspection , because they make them so let them do the testing and send us results , i would really love to see their side of the story


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Sat Jul 22, 2017 7:10 pm 
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TKB4 wrote:
I do find it interesting that the failures on two were 200 miles one 700 miles and one 4,000 miles after work but of course correlation and causation are not the same. Otherwise one could conclude that ARP stud replacement or replacing rockers (BTW were they replaced with the new version?) or adding the weeks kit were causes.

I tried to follow this logic trail, but it failed for me.
1) Without being there to know PRECISELY what work was done, by whom, and following what procedures, not only causation fails, but correlation as well.
2) If I were to assume that major work had been done, the most common major work needed is timing belt change, and associated maintenance. This, if proven true, could possibly be the one thing that these four examples might actually share. Would it not then be more reasonable to look to human error, or deliberately cutting procedural corners, while performing the re-timing sequence? I don't understand, when, having slippery logical footing already, one would not slide, but jump down-slope, to attempt hanging the blame on ARP studs or WEEKS kits. Both ARP studs and WEEKS kits are on dozens if not hundreds of CRD's that haven't had valves break for, many millions of combined miles. Now people who make mistakes while performing complicated procedures, including the mistake of having someone else who makes mistakes, do the work, is immensely more common.


The one valve failure under the previously broken rocker makes sense on one level maybe the rocker didn't really do its job.

I do personally wonder if a speciific combination of rocker and arp studs could even contribute. I am fixing to either replace just ARP or ARP and head gasket depending on what i find on teardown. I was planning on replacing rockers also with either scenario. Is the design so tight that further compression of the head gasket with ARP s and new rockers that are not worn could essentially reduce clearance enough to be out of tolerance?

Far more likely that the wrong thickness head gasket was used. Overtorquing the ARP studs is possible, but that by it's self still wouldn't bury the valves into the pistons. It could, however, compress the head gasket a tiny bit more, but not nearly as much as using the wrong head gasket.

I would say no, since the valves also have wear which would increase it some compared to new engine. Are the new rockers actually oiling better? If the ARP s and rockers were being replaced prophylactically I can see this as a very remote possibility. If they are being replaced after broken rockers I would personally expect sometimes the valves were unknowingly stressed or damaged. Maybe I shouldn't fix the head gasket leak and just run it till it failed catastrophically!!!! LOL! :ROTFL: I am afraid to touch it and spend all the time and money then have it fail in 200 miles! Aren't we all? Thankfully I have overcome the fear and am proceeding with the repair. If a brand new head did it I will take my chances.

I will report after 1,000 miles if I make it that far! Hopefully you will still be reporting many thousands of miles later.
I wish you the best of luck. And wish you to make your own luck. Do things in correct order. Double check things as you go. Take notes when you have to consult the manual, or, heck I guess if you have a smartphone you can have them right with you. If you get distracted or have to take a break, back up a step or two, and go through what you did up to the point you left. The time you spend doing this will be a heck of a lot less than the time you could spend having to go way back and install some small but very important part that got overlooked. (Like getting an engine completely rebuilt and assembled and realizing that wonky looking washer over there is actually the crankshaft oil-slinger)

_________________
'06 Lbrty Sprt CRD 147Kmi

Sasquatch
DSS Turbo
CAT-elimntr
Weeks Stg1&2 EGRfix
PV-200
BLING
vent gauge mount

IDParts New
head
cams
rockers
Timing set
ARP studs
eTn1 GX2123 5v GPs

Flowmaster 942550
Carter P76611M
GM 12611872
Hayden 2986
GM 15017911
2010 Trans
Sonnax 44957
Transgo kit
AHS 45T TC
Cooper 51770

Future plans: GDE Trans&Hot-tune


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Wed Jul 26, 2017 4:29 pm 
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rankom wrote:
ok back on this thread again ,, so my understanding is that exhaust valves are made in VM factory in Istanbul Turkey , i think for the people that experienced these RARE failures (broken valve) , I think it is worth contacting the manufacturer and sending them faulty valves for inspection , because they make them so let them do the testing and send us results , i would really love to see their side of the story

Are all valves for this engine made by the SAME manufacture in the same location?
If not, you may be on to something as to why we hear of some failing while some never do.... :roll:

I fail to see how the Week elbow kit should even be in the mix on this subject! I would be very hard pressed to be convinced that it could possibly have anything to do with a valve failure! :shock:

_________________
05 Jeep Liberty CRD Limited :JEEPIN:
Blk Brush Guard/Hella's/LED's
Ironman Springs/Bilstein's
Yeti Stg4 MaxTune
Weeks ElbowKit/Battery Tray
NO FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pump
2mic.Sec.Fuel Filter
Flowmaster/NOcat
V6 Airbox
GM11 blade fan/Hayden HD clutch
Ironrock Trilink
98 Dodge Cummins, 5"exh. Viair,K&N


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Jul 27, 2017 12:31 am 
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Sending to VMM is the worst possible thing you can do if you want to get a truthful failure analysis.

Your physical samples / evidence will be "lost in the mail" and guaranteed, they will "have no idea what could have happened to them"

This is not a current engine design, so they have no interest in solving this issue. In fact, their only interest with this engine design is to sell the rest of their part stock, and hide every possible bit of evidence there ever was a problem.

And yes, I do have sufficient manufacturing background to know how corporations deal with these things. Perhaps not all.. but most.

To find out the truth of why they fail, is actually what Jim did - Take them to an impartial third party with the capability and expertise to look at the evidence and give an educated opinion based on that.
We already know the sample isn't big enough to determine what percentage of failure is due to one thing or another.
I just want to know if there is some particular thing we can do, up to and including having custom valves made out of, what material, to give a large enough margin of overkill, that makes the risk of failure, negligible.

_________________
'06 Lbrty Sprt CRD 147Kmi

Sasquatch
DSS Turbo
CAT-elimntr
Weeks Stg1&2 EGRfix
PV-200
BLING
vent gauge mount

IDParts New
head
cams
rockers
Timing set
ARP studs
eTn1 GX2123 5v GPs

Flowmaster 942550
Carter P76611M
GM 12611872
Hayden 2986
GM 15017911
2010 Trans
Sonnax 44957
Transgo kit
AHS 45T TC
Cooper 51770

Future plans: GDE Trans&Hot-tune


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Fri Jul 28, 2017 9:16 pm 
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Location: New Orleans, Louisiana
If i wasn't so broke buying jeep parts, this would be posted here from my onedrive. You can just read the abstract for free. They want 35 bucks for the article. may not be any good but it's on topic

Failure analysis and metallurgical investigation of diesel engine exhaust valves

http://www.sciencedirect.com/science/ar ... 0705000828

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2005 Jeep Liberty CRD 110k miles - working on tb, rockers, arp, camshafts
1985 Mitsubishi Mighty Max 2.0 liter
1989 Vanagon GL


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Fri Jul 28, 2017 9:41 pm 
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That is interesting! Also interesting is that none of the failures involved head separation.
These look more like the "common" failures I've seen in other engines over the years.
Valve fails, limp it in, have the head rebuilt, and off ya go.
Not this sudden 'bang' and you need an entire new head that costs the same as any other complete long block, plus piston, ljner, etc etc.

_________________
'06 Lbrty Sprt CRD 147Kmi

Sasquatch
DSS Turbo
CAT-elimntr
Weeks Stg1&2 EGRfix
PV-200
BLING
vent gauge mount

IDParts New
head
cams
rockers
Timing set
ARP studs
eTn1 GX2123 5v GPs

Flowmaster 942550
Carter P76611M
GM 12611872
Hayden 2986
GM 15017911
2010 Trans
Sonnax 44957
Transgo kit
AHS 45T TC
Cooper 51770

Future plans: GDE Trans&Hot-tune


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Fri Jul 28, 2017 9:44 pm 
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anyone can google "valve failure", but this one isn't infested with pop-ups and advertising (and it's free)

https://www.rroij.com/open-access/failu ... ?aid=44965

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2005 Jeep Liberty CRD 110k miles - working on tb, rockers, arp, camshafts
1985 Mitsubishi Mighty Max 2.0 liter
1989 Vanagon GL


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Fri Jul 28, 2017 9:57 pm 
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my 2005 head has what appears to be a "born on" date stamped just to the rear of the #1 glow plug on the head.

check it out https://1drv.ms/i/s!AjoXnVa96mPNmIh2vYhjCR4MUm8brA

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2005 Jeep Liberty CRD 110k miles - working on tb, rockers, arp, camshafts
1985 Mitsubishi Mighty Max 2.0 liter
1989 Vanagon GL


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Fri Jul 28, 2017 11:48 pm 
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Both of mine have that too.

I don't know if it was the date of assembly or the date of machining, or the date of installation, but it should be consistent for all of them, whatever it is.

_________________
'06 Lbrty Sprt CRD 147Kmi

Sasquatch
DSS Turbo
CAT-elimntr
Weeks Stg1&2 EGRfix
PV-200
BLING
vent gauge mount

IDParts New
head
cams
rockers
Timing set
ARP studs
eTn1 GX2123 5v GPs

Flowmaster 942550
Carter P76611M
GM 12611872
Hayden 2986
GM 15017911
2010 Trans
Sonnax 44957
Transgo kit
AHS 45T TC
Cooper 51770

Future plans: GDE Trans&Hot-tune


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Sat Jul 29, 2017 9:52 am 
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minnisp wrote:
anyone can google "valve failure", but this one isn't infested with pop-ups and advertising (and it's free)
https://www.rroij.com/open-access/failu ... ?aid=44965

Thank you very much for the link! A very good read that reinforces what some on LOST have been saying all along.
It is a shame the picture links on the Web page do not work (404) :(
I figured out if you click on "View PDF", you can see the pictures in the article and save the article for future reference if you so desire... :wink:

The main takeaway in the article: Fatigue failure is the main cause of valve failure. The fatigue strength is significantly decreased with increase of temperature.
The article does a good job of explaining how high temperatures over time can cause fatigue, stress cracking, and eventual failure!
I am of the opinion that temperature plays a huge roll in the valve failures and / or head cracking that some have unfortunately had happened to them... :roll:

_________________
05 Jeep Liberty CRD Limited :JEEPIN:
Blk Brush Guard/Hella's/LED's
Ironman Springs/Bilstein's
Yeti Stg4 MaxTune
Weeks ElbowKit/Battery Tray
NO FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pump
2mic.Sec.Fuel Filter
Flowmaster/NOcat
V6 Airbox
GM11 blade fan/Hayden HD clutch
Ironrock Trilink
98 Dodge Cummins, 5"exh. Viair,K&N


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Sat Jul 29, 2017 2:09 pm 
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Going to the machine shop on Monday to have him inspect the head, and check the valves under these collapsed rockers. Lucky to have a diesel machine shop here in New Orleans. "Darr Engine Service" is the name if you're in the area looking for a machine shop.

Torque wrench failed (craftsman) trying to get torques for the head bolts. no clicky. All i can say is that there was a lot of variation and it seemed to have lower torque on the intake outer bolts of 2, 3 and 4. I ordered a CDI but too late for head removal.


valves cylinder 1 (coolant?)

https://1drv.ms/i/s!AjoXnVa96mPNmIkBY6oA2-TSM8yK-w

valves cylinder 2 (note dead glow plug, this also had a collapsed exhaust rocker)

https://1drv.ms/i/s!AjoXnVa96mPNmIkCwDoVWh5EfSrb0g

valves cylinder 3

https://1drv.ms/i/s!AjoXnVa96mPNmIkDUsPiux4L5PzdCA

valves cylinder 4 (collapsed rocker on the last exhaust valve).

https://1drv.ms/i/s!AjoXnVa96mPNmIkE4XwCglmg9hJHuA

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2005 Jeep Liberty CRD 110k miles - working on tb, rockers, arp, camshafts
1985 Mitsubishi Mighty Max 2.0 liter
1989 Vanagon GL


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Aug 10, 2017 7:09 pm 
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Machinist reported that he milled the head to eliminate some surface warp around cylinders 2 and 3, as well as slight fire-ring impression. He cut a little less than .003. The valve seats were not concentric with valve guides on 2 and 3. he recut the seats so they're concentric with the guides, and in coordination with the surface milling. From removal, bolts for cylinders 2 and 3 were not correct torque, significantly looser than the front and rear cylinder head bolts. So he described a scenario where the seat/guide misalignment could cause lateral forces on the stem/structure of the valve during both opening, and closing, leading to long-term and ever increasing fatigue. I though it was worth posting here and see what you make of his theory. I like his thinking. if true, and if similar warpage occurs on other crds, it could explain at least some of the valve failures.

NOTE: if someone has already posted this theory, then my machinist agrees with you, and so do i :)

The scenario would be:

1. the fastener begins to fail or was never properly torqued
2. the head over time begins to warp due to uneven clamping forces, heat etc
3. the movement of the structure of the head changes the position of the seat relative to the valve guide (he called it "sinking")
4. increase in valve misalignment induced lateral force on the valve stem during opening and closing
5. valve suffers increasing fatigue and eventual failure.

Have fun!

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2005 Jeep Liberty CRD 110k miles - working on tb, rockers, arp, camshafts
1985 Mitsubishi Mighty Max 2.0 liter
1989 Vanagon GL


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Aug 10, 2017 8:35 pm 
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Sounds plausible.

The movement would be very very slight, and possibly varied. That could explain why some last longer than others.

If it is the case, proper installation and torquing of ARP studs should absolutely stop the movement.

With this in mind, when mine requires a new timing belt, I think I'll lift the intake manifold / valve cover off and retorque the head nuts again to make sure none have loosened or lost tension somehow, and check the rockers while I'm there.

_________________
'06 Lbrty Sprt CRD 147Kmi

Sasquatch
DSS Turbo
CAT-elimntr
Weeks Stg1&2 EGRfix
PV-200
BLING
vent gauge mount

IDParts New
head
cams
rockers
Timing set
ARP studs
eTn1 GX2123 5v GPs

Flowmaster 942550
Carter P76611M
GM 12611872
Hayden 2986
GM 15017911
2010 Trans
Sonnax 44957
Transgo kit
AHS 45T TC
Cooper 51770

Future plans: GDE Trans&Hot-tune


Last edited by GordnadoCRD on Fri Aug 11, 2017 3:32 am, edited 1 time in total.

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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Aug 10, 2017 9:56 pm 
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Better than some theories I have read! :wink:
thanks,

_________________
05 Jeep Liberty CRD Limited :JEEPIN:
Blk Brush Guard/Hella's/LED's
Ironman Springs/Bilstein's
Yeti Stg4 MaxTune
Weeks ElbowKit/Battery Tray
NO FCV/EGR
Samcos/ProVent
SunCoast/Transgo
Carter Intank-pump
2mic.Sec.Fuel Filter
Flowmaster/NOcat
V6 Airbox
GM11 blade fan/Hayden HD clutch
Ironrock Trilink
98 Dodge Cummins, 5"exh. Viair,K&N


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 Post subject: Re: Valve failure research thread - We need your data!
PostPosted: Thu Aug 10, 2017 10:09 pm 
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Posts: 33
minnisp wrote:
Machinist reported that he milled the head to eliminate some surface warp around cylinders 2 and 3, as well as slight fire-ring impression. He cut a little less than .003. The valve seats were not concentric with valve guides on 2 and 3. he recut the seats so they're concentric with the guides, and in coordination with the surface milling. From removal, bolts for cylinders 2 and 3 were not correct torque, significantly looser than the front and rear cylinder head bolts. So he described a scenario where the seat/guide misalignment could cause lateral forces on the stem/structure of the valve during both opening, and closing, leading to long-term and ever increasing fatigue. I though it was worth posting here and see what you make of his theory. I like his thinking. if true, and if similar warpage occurs on other crds, it could explain at least some of the valve failures.

NOTE: if someone has already posted this theory, then my machinist agrees with you, and so do i :)

The scenario would be:

1. the fastener begins to fail or was never properly torqued
2. the head over time begins to warp due to uneven clamping forces, heat etc
3. the movement of the structure of the head changes the position of the seat relative to the valve guide (he called it "sinking")
4. increase in valve misalignment induced lateral force on the valve stem during opening and closing
5. valve suffers increasing fatigue and eventual failure.

Have fun!


If you are still working on the vehicle, do you have any images of your exhaust valves? Mine are quite necked down where they come out of the guide, and have concentric rings, then it gets thicker right at where the flute joins. I'd be interesting in comparing images.


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