The incredible LB7 exploding valve...

[h2oskibumz]

Just thought I would post up some "fun" pics acquired over the past couple of days.

http://img233.imageshack.us/img233/9850/im001335.th.jpg (http://img233.imageshack.us/i/im001335.jpg/) http://img233.imageshack.us/img233/305/im001333.th.jpg (http://img233.imageshack.us/i/im001333.jpg/)

We think we may have had an injector failure in #7 which caused that cylinder to lean out causing excessive heat buildup. Eventually, heat caused the valve to warp or crack… causing loss of compression and even MORE heat buildup. Ultimately the valve shattered and the pieces bouncing around in the cylinder pretty much finished the job.

Fun stuff!

Thanks to Rick Lance for all the sage advice. Rick listened to the truck the day after it happened and told me that he thought it may have grenaded a valve. In the next breath he promptly offered up whatever he had that I could use to put it together… THANKS MAN!

Also thanks to Brian (hondarider) who offered up his spare heads and whatever else I may have needed from him at a great price…

…and to all the posters who’ve been filling this place up with knowledge. I’ll be using lots of Henry’s latest postings from the flurry of GM Tech document postings he’s done the last week or so… We are a long ways from having this back together, but without these guys and dmaxcentral I would have been ABSOLUTELY lost…

[neversatisfied]

Ouch! That does not look pretty. Hope you get it back together soon.

[RickDLance]

Ouch! I'm kind of sorry I was right. :( Did it scar the cylinder wall?

[h2oskibumz]

Did it scar the cylinder wall?

No, it did NOT.

In the grand scheme of things I was lucky, though the other motor I bought is JUST a parts motor... I should come out OK stealing the one piston and head off that motor, and honing the cylinder.

[h2oskibumz]

Ouch! That does not look pretty. Hope you get it back together soon.

x2 Dude... <goofy redneck grin smiley here!> ...thanks!

[Fingers]

That is simply a valve failure. Unlikely it was caused by heat. Maybe a piece of debris got caught under it when the piston cam up and "seated" the valve? See if there is a witness mark on the valve seat where the piece is missing.

Your lucky if it didn't eat the bore. With a little luck, you can get away with a piston, rod and valve job.

FWIW, there is no such thing as "leaning it out" on diesels. Actually, the less fuel, the cooler.

[CBRJohn2000]

FWIW, there is no such thing as "leaning it out" on diesels. Actually, the less fuel, the cooler.

Thats what I was just thinking....just in a different MONKEY sort of way! In my mind diesels run on a fuel to air mix rather than an air to fuel mixture like gasoline. (I know....the mind of a MONKEY is scarry! ;))

[ripmf666]

I will have more info posted in the next few days around 9 pages to go lol.

[h2oskibumz]

Thanks Jon... one more thing that doesn't translate well from gas to diesel I guess... I appreciate you helping me understand, and believe me, I KNOW just how lucky I was that it didn't do further damage...

I don't plan to have this head fixed right away, just switching it out with another one. I may have it worked later, but there will definitely have to be some repair of the head itself, lots of missing/extra material.

The truck is down in my college roommate's shop... Once I get back down I'll look for the mark...

[h2oskibumz]

OK, I hadn’t visited this thread in a while; perhaps I owe an update…

After parts location delays, and a couple of boneheaded mistakes on my part, this thing is all back together... I'm thought I would share some additional thoughts for anyone that may be interested.

First, I am a liar... sort of. I said this was #7, which had a decent balance rate. I made that statement based on… small block experience. Once this thing was upside down and the pan was off, I learned that it turns out that on the Duramax the ODDS are on the passenger's side and evens on the driver's side... so it was actually #8 that melted/broke the valve. The same #8 which had HIDEOUS looking balance rates...



That is simply a valve failure. Unlikely it was caused by heat. Maybe a piece of debris got caught under it when the piston cam up and "seated" the valve? See if there is a witness mark on the valve seat where the piece is missing.

Jon, since I used a set of heads from Brian (hondarider) I didn't tear down that valve. I should have, but forgot. So I can't tell if there is a witness mark or not. There is a good size chunk of that seat missing anyway so there is a good chance that I couldn't tell. I’ll take it as “homework” to get that valve pulled out and get some better pictures…

Your lucky if it didn't eat the bore. With a little luck, you can get away with a piston, rod and valve job.

Well, we tried to get away with that. We waited 10 days to get rings for that hole... then found out when I went to see Rick for a piston that he HAD a set of 8 that he had to "borrow" 1 set out of, so he gave me 1 cylinder worth to use in case the ones I ordered from GM didn't come through... they did, so I was going to use the GM ones and get Rick his back...

Where we REALLY failed is that we failed to pull that piston out before ordering parts. So, when I finally had all the parts together and went down to ring the one new (used) piston and put it all back together only to find the wrist pin bushing on that one was WAY loose. It might have been OK, but... at that point, if one is that loose, the others probably are too... so I called Rick, knowing he had the other 6 sets and "borrowed" the rest of his rings. I also ordered bushings from Eric Merchant, but this mistake cost us a week...

So in the end, we went with 1 used piston, 1 hole w/ GM rings, 7 holes w/ Rick's Perfect Circle rings, all 8 new wrist pin bushings, new rod bearings/bolts, new main bearings/bolts, a new oil pump, a used set of heads, a new set of injectors... and a whole lot of incidental casualties (gaskets, flexplate bolts, o rings from hell, etc...) and its all done and SEEMS to be working well.

Hey, at least it didn't need that rod!!!


FWIW, there is no such thing as "leaning it out" on diesels. Actually, the less fuel, the cooler.

OK, then based on my earlier “lies” about this coming out of a cylinder with good balance rates, perhaps this still comes back to injectors. I have an EFI Live log file showing that #8 was around -5.0 (along w/ number 2) in Park and pegged at 7 (as high as EFI Live reads) once in gear with your foot on the brake.

Given that, I think that it could be the polar opposite of my original theory… as in #8 injector failed dumping REDICULOUS amounts of fuel into the cylinder… things get hot hot hot, and something gave. There was a good sized chunk of piston cracked off… I think that perhaps IT broke off first and got under the valve, or perhaps the valve did get hot and break first…

Either way, it goes without saying that without Rick Lance’s advice and help w/ parts and tools I would still be trying to figure out what to do…

[RickDLance]

So is it running? :D

[h2oskibumz]

YES!!!

After getting the rods back from the machine shop Wednesday afternoon, I went down Thursday morning. We spent the rest of Thursday doing the bottom end. Friday doing heads, adjusting valves, and hanging on valve covers, CP3, water pump, fuel rails and related, oil cooler, intake, and turbo. Saturday morning putting the wiring all together and hang on the exhaust and then started back into the truck. Spent late evening Saturday bolting up the trans, putting the CAC and its piping back in, core support, etc.

We had it all back together by Saturday night, save the radiator and batteries, got that done Sunday and fired it up... Had a little trouble with fuel... leaking filter, sucking in air... It was a new filter so I was not going to change it (only had about 2k miles or so) and no one remembered having it off the housing... None the less, the cup/donut (not the main o-ring but the little one that sometimes sticks) was missing. Looking back I'm thinking I NOW remember that we had it off for clearance coming out and screwed it back together once it was out... somehow we lost the rubber cup at that time.

Once we put a new filter and reprimed, everything seemed to work great. It started right up and ran 1000-1500 RPMs for 2 hours (stick and power seat idle adjustment method 'cause I couldn't figure out how to set the idle w/ EFI Live's Scan tool. I THOUGHT it was in the bidirectional controls but nothing there was accessible to me.)

I only drove it 30 miles Sunday afternoon and left it w/ Tim. We figured that him driving it back and forth from home to the farm (60 mile round trip) and a couple of trips to town (30 mile round trip) every day he could put some good miles on... A good mix plenty of hills, curves, a little town driving and a lot of wide open County Highway driving would be a good break in... Certainly better than ME jumping in it and driving it home 150 miles...

If all goes like it went Sunday and yesterday, then he is going to bring it up to Columbia for me tomorrow, and I might bring it to KC tomorrow night (return your tools and log some more miles). We'll have to see how it goes after driving it today and then decide, but I think we might have got her done!!!

[RickDLance]

Congrats!! :thumb:

[01LB7]

I know this is an old post, but what did it sound like when this happened, my truck last night started knocking horribly bad last night and it's obviously from the pas side, no smoke and now codes, misses, and makes a bad chugging sound from the stack, several theories but not sure yet thanks in advance

[RickDLance]

Where's your truck at?

[01LB7]

I'm in Maysville, MO about 15min northwest of cameron