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[mikeminnillo]

ok, heres my reposts from a couple threads i made on the vortex.  first was from about a week or so ago, second post is from today, after i tried driving my car home from my gf's house.  

FIRST POST:
ok, heres the relevant info on the car:

MKIV 12v turbo @ 9 psi
eurospec sport 268 cams, rest of head is all stock
97k miles
timing chain/tensioners/guides done @ 85k miles


the problem im having is a knocking type sound. it happens when the car is warm or cold, and at all rpms. the frequency of the noise is most definitely rpm dependent, and at idle, i can feel something like a knocking on the valve cover. it feels like the knocking is coming from near cylinders 5&6 or near the timing chain. the noise is very loud and noticeable, and at anything over 2500 rpm, it sounds like a damn machine gun.

i pulled off the valve cover to see if anything looked odd, and there was oil in there like there should be. no metal shavings, nothing that looked broken. everything looked fine.

there doesnt seem to be any misfire, as ive have that problem before, and am not experiencing any related symptoms. the car is not down on power at all, either, as far as i can tell.

any help would be greatly appreciated. i would prefer not to tear the head apart, but if i have to, then so be it. ive stopped driving the car for now for fear of causing further damage. thanks in advance for any help you guys could provide.

SECOND POST:
well, yesterday i was trying to drive the car home from my girlfriend's house (where the car was kept since the knocking started), and en route, the car decided it had had enough.  i felt a clunk, lost most power, and started spewing oil smoke out the exhaust.  towed the car home and began tearing into things to figure out what the problem was.  here's what ive discovered so far:

all 6 spark plugs were covered in oil
spark plug on cyl #5 is destroyed (see pic below)
looking down the spark plug hole of cyl 5, i can clearly see a valve in front of the spark plug hole.
there is now oil leaking out of the intake of my turbo
the turbo feels mostly seized


so heres my theory of the order of events of what happened.  feel free to correct me as you deem necessary.  

a. something caused valve to bend/break
b. valve eventually made contact with spark plug
c. contact with plug destroyed plug and damaged valve guide, causing oil to leak into the cylinder
d. parts of the broken spark plug made their way out the exhaust port and into the turbo, destroying the turbo
e. car=dead

so, my question is:  where do i go from here?  my thoughts are to pull the head, assess the damage, have head repaired, replace turbo, put everything back together with a head spacer and ARP hardware.  does this all sound reasonable?

any other help or advice would be greatly appreciated!


spark plug carnage

[Gallep]

Oh noes....

Well your game plan sounds good, but I'd be hung up on your first event, "something caused valve to bend/break".  I would try thinking back as to what you might have done driving, maintenance, or wrenching wise that could have caused such an event.  Maybe just a failed Valve Keeper thingy started all this...

Or maybe, just maybe, if you had 24 valves, this would have never happened 

[Barry]

Who changed your timing chain?


Why the fuck did you try to drive it home after you heard a bad nosie?


 

[mikeminnillo]

gabe from blue water did the timing chain.  but that was a year and a half and many miles ago, so i doubt that there was an issue with the timing chain work that he did.  i decided to drive it because despite the noise, it was driving just fine.  i was even able to give it a little boost, and seemed to be functioning fine. 

[Barry]

Ok... I am sure Gabe did the chains right...


Still man... sucks that you have to replace almost everything now.

If it was me, I'd pull the head, and check your cylinder walls... hopefully that spark plug didnt mess up the bottom end too.

[Smokestack]

Send the head to the machine shop for rebuilding/checking and check to see if there's any scoring in the cylinder walls. If so, get ready for a rebuild of the bottom end too. There's a couple of OBD2 VR heads down at UPAP right now.

I'd be concerned with how the valve bent to begin with. If the guide was worn enough to cause the valve to bend you'd be dumping oil into the combustion chamber and smoking like a freight train. I'll bet either a valve keeper failed (or possibly valve spring causing the valve keeper to come free) or one of the guides/tensioners failed causing it to jump a tooth.

[Barry]

fuck the rebuild.... throw that head in the trash can and go buy one at pull and pay.


I was intially thinking you jumped a timing tooth because a tensioner gave out, or because the chain stretched....


One advantage OBDI (of many) has over OBDII, is that on the VR, the timing chain is double link, and not a single link chain.

Then I started thinking about my mkII. The motor is an OBDII VR with 276 cams in it. I started talking about boost, and one of my buddies who is a pretty damn good VW technician noted that the cams would potentially float the valves at a higher RPM range and could push the valves into the pistons.... something to consider

[101stvet]

I love sparkplug carnage ...my rabbit did that to a plug once didn't destroy anything thou...and the corrado just did the samething still don't know what caused it.....

[Barry]

One more question....



Did you not put HD valve springs in, when you put the cams in?

[Smokestack]

A 268 is a pretty mild cam. Unless VR valve springs are shit they should be able to handle it.

[mikeminnillo]

i was running stock springs.  and for the time leading up to the carnage, i wasnt revving the engine high at all.  hell, since ive been back from my deployment (3 weeks) i dont even think ive revved past 6500.

[greggearhead]

Then I started thinking about my mkII. The motor is an OBDII VR with 276 cams in it. I started talking about boost, and one of my buddies who is a pretty damn good VW technician noted that the cams would potentially float the valves at a higher RPM range and could push the valves into the pistons.... something to consider

Um, boost won't float your valves any more than altitude will. 

[Barry]

I didnt think so either Greg... but it's something I never thought about...


Could it be possible, that the combination of cams, and stock valve springs plus boost would cause valve float to the point where the valve would hit the piston? I imagine it would be, seeing how the motor revs alot quicker under pressure than it would as a N/A application


I could be wrong, and to be honest, I am fairly ignorant, but I will talk to Chris at C2 before I put any kind of forced induction on my cammed out VR...

[greggearhead]

Nope.  Boost "pushing" open valves is a complete fallacy, unless we are talking about competition diesels using 100-150psi of boost, that have weak springs and are revving way beyond normal design parameters for the engine.

A spring that is strong enough to control valve float at 7000rpm isn't gonna fail to control the valve becuase there is 20-30% more airflow, or a slightly higher pressure differential.  Besides, with the valve open, the additional airflow isn't acting much on the valve itself.  If it was closed, and you could force 100psi into the port, you might pop the valve a tiny bit, but it would quickly close up again.  Not the same dynamics to what we are talking about anyway.

At least, in my opinion.  I'm happy to be proven wrong and learn some more. 

[Barry]

Duly noted!


I'll let you know what Chris says too... I would love to keep the big cams in the big valve head, but really dont want to chance damaging a $2500 head for 12 lbs of boost.

[Smokestack]

Boost shouldn't float the valves. If you think about it, the amount of pressure in the combustion chamber is slightly below or way above the pressure in the intake track whether it's boosted or NA. Only way to change it is to make the valve opening stupid small or the piston diameter and/or stroke stupid big.

Since your car sat for awhile when you were deployed it almost makes me wonder if all the oil bleed out of the lifters and tensioner and either prematurely wore/broke the guides, or made it take too long to rebuild up oil pressure in the tensioner causing it to jump timing a tooth.

I'll let you know what Chris says too... I would love to keep the big cams in the big valve head, but really dont want to chance damaging a $2500 head for 12 lbs of boost.

Only thing to worry about with big cams is valve overlap. Big lobe cams tend to have a lot, and that tends to blow a lot of the hard earned pressure your turbo worked on out the exhaust. It can also screw with O2 readings showing a leaner condition than what's actually there.

[scurvy_bandit]

I go with Barry's suggestion. 40 dollars for a head from UP&P beats overhaul anyday.  That head is trashed, turn it into scrap and get some money to buy beer with.

[mikeminnillo]

got to work and pulled the head off today.  you guys asked for carnage, and these pics are sure to deliver.  at this point, im not sure of how what happened actually happened.

so, first, i pull the head and find this:





and then, i check for any piston/cylinder damage, and find this:





so, im kinda questioning where to go from here.  if you look at the cylinder pictures, you can see that there is actually material missing from the bottom of the cylinder walls.  so, im wondering if its even worth trying to save this motor, or if its time to scrap it and try to move on to a new motor.  obviously, the head is junk.  i dont see that as save able.

any ideas from here?

[Gallep]

Awesome!  I'd start over as well with a new motor.

BTW, Where's the Piston?

[mikeminnillo]

my guess is that the piston is ground up into a bunch of little pieces in the oil pan somewhere

[Gallep]

my guess is that the piston is ground up into a bunch of little pieces in the oil pan somewhere

Badass, post pics of the oil pan contents if/when u drop it.

[Smokestack]

Wow! How do the other pistons look? I'm curious as to if it was detonation causing piston failure, or the piston just giving up the ghost. Either way, that's a boat anchor there. Go to UPAP and pull one of the VR's down there and start over.

[greggearhead]

Yep.   That motor is done.  Anything is savable, but that isn't a Bugatti.  Isn't worth the price to resurect it. 

You could pull a 'Ryan' and build the shit out of it for lots of boost, but those wrist pin grooves in the cylinder bores look too deep to save....

[SwiftMKIII]

I call detonation, then the rod beat the crap out of the rest of the piston.

Well done Mike, that's the stuff that makes Turbos fun.

[xbluewaterx]

Mike it seems like you need larger injectors to feed that thing and a software upgrade. That is unless you plan on running around 10psi forever.