Head and Cylinder Issues

[78Chev]

I have been plagued with a knock ever since I had the engine built. One of the causes was the oil pickup hitting the pan. I actually found scuff marks on the pan. Moving the pickup helped some but still had the knock. Swapped injectors until I could do it without thinking. Even changed lifters while engine was in the truck. Got tired of it all, so I pulled the engine and tonight the left head (always seemed to be loudest at #7 with a steth on the exhaust manifold). I have taken pictures of what I found and posted at:

Engine Pics Here

Images e, f, and o are pretty telling. It looks to me like the intake on #7 is leaking oil into the cylinder which is running down the underside of the head toward the pre-cup. The buildup on the head is about .012 thick and looks to be crusty oil. There is also a slight buildup in the matching area on the piston. I'm guessing the knock comes from contact of the piston and head build up areas, but not sure. Looks like the oil washed away the carbon buildup on part of the cylinder side wall where the oil is leaking out of the valve.

I'm planning on having the valve fixed and the rest of the head checked. I might do the right head while I'm at it too. My concern is that the rod bearing might be affected so I will check that out too.

I'm no expert. Do you think my diagnosis and fix are correct? Any other explanations? What other things should I be concerned about and look for? Thanks
- Randy

[ 05-18-2005, 03:55 AM: Message edited by: 78Chev ]

[john8662]

So, you're thinking right now that the cause is because you have a bad valve stem seal thats allowing abnormal amounts of oil to enter the combustion chamber. This extra oil is then causing the knock because there isn't sufficient room for oil and the smal amount of area during combustion/detonation?

Sounds like you've been busy, doing some of the same things I've been doing, the lifters thing blows me away, ton of work eh?

How did the engine run besides the knock you were hearing? Good power, good idle, what kind of oil consumption were you seeing?

[78Chev]

Thanks, John. I did the lifters in the truck some time ago - I was revisiting that experience in my mind when I read your posts about doing the same. NOT A FUN JOB (My back still hurts - but it does make us feel like surgeons!) There is a lot of talk about lifters acting up but in my case it was clearly not a lifter or an injector.

It actually ran pretty good but this winter it was smoking quite a bit on start up (and missing) then it would all of a sudden clear up. That made me suspicious of a valve issue. But like you the constant tick/knock and bit of rough idle drives me absolutely crazy. I'm not sure where the oil is coming from - I would guess the valve stem. The cylinder shop should be able to let me know. I'm hoping that the knock is not the rod bearing, possibly damaged from the head and piston colliding where they had build up. Hope also that it is not the wrist pin.

One other thing that I found was that after I installed the energy suspension motor mounts (same as Casey just did) that I felt an increased vibration. I just inspected them and noticed that the upper mounts only contact three of the metal tabs on the poly bottoms - on both sets. I suspect that the vibration of the engine caused intermittent touching of the fourth tab causing the vibration. The uppers contact all four tabs on my old rubber mounts. Always something...

Randy

[john8662]

Also something to tell the machine shop working on your heads is to pay close attention to the valve guides. I'm glad you made this post and took excellent pictures! I'm starting to wonder whats wrong with my engine too, and I'm up to the point of yanking it and pulling it apart (no more guessing). But I've got to wait until I can get the 6.5 going again.

Keep us posted on what they end up finding is wrong with the heads.

Since you have the engine on the stand, perhaps it would be good insurance to pull the pan and plastigauge #7 rod bearings at the least, a visual inspection. I seem to think that in this case that the wrist pin would be stronger than the bearing material, so it's probably ok.

[78Chev]

Will do the plastigauge for sure on the rod bearing. Glad to know that the wrist pins are less likely to fail than the bearing material.

Also, would you look at image F (click on it to enlarge it)? See the vertical scratches that dip just below the top ring line? Do you think this is an issue? I can't feel them but they are noticeable to the eye. Don't really want to have to take this apart and hone it.

[john8662]

I can't say that I'd re-hone the cylinder, because that takes meat out of the cylinder and changes your piston to bore clearance. I can't see what you're describing, I do see the top ring mark, and some very good honing marks. If you can't feel it with your fingernail, it's probably not an issue.

[78Chev]

Well, the cylinder head shop said the valves, guides, etc. all looked great. The intake on #7 was perfect (I saw it myself). The heads are not GM but new castings. The guides had never been nerled (sp?) - new and in great shape. The guy there (owns the shop; been there forever) said that the oil was NOT coming from the head but suggested that it might be a problem with the oil control ring.

So it looks like I get to take the piston out. I'll need some help from you guys here once it's out on checking and changing the oil ring (and compression if need be), whether I need to hone again, etc., etc.

Randy

[john8662]

Randy,

Did you take a compression test before pulling the engine? I'd be interested in what you found there. You say the heads are not GM, I'm a little afraid of that... I bought a set of "new" casting heads, but was discouraged in the quatlity of the cast of these heads. I was informed by Benny at Avant that they were Chinese casted heads. I bought them out of Alabama, and returned them.

But, that doesn't really mean that they are bad heads. You could very well have a bad/stuck oil ring. It will be the lowest ring on the piston, I don't know much about R&Ring rings yet. Maybe Casey will chime in here shortly as he is in knee deep into his 6.2 rebuild.

Also, what did the machine shop say about the possibility of bad stem seals?

[78Chev]

Unfortunately I did not do a compression test. On #5 piston I just notices a pimple which stuck up pretty high. Not sure if it was hitting the head. I removed it and found that there was an air pocket above it. Will post pics later.

I have a theory: I have a dual plane intake manifold. On the odd (left) side of the engine the plane in the manifold is lower than the right, and since the engine tips backward a bit oil from the CDR system will naturally flow to the #7 intake port. Maybe it can or has accumulated there when the valve sat open overnight? Just trying to figure out how the oil got in there if it is not the oil control ring. I always have a lot of oil in the intake manifold from the CDR system.

[DmaxMaverick]

I, too, wouldn't point at the exhaust valve for the source of the oil. Much more likely another source, such as the intake like you say. Regardless of how the oil got in there, I don't think it would cause a knock as you describe. There doesn't appear to have been enough oil to cause a detonation knock. The carbon/oil trail on the head is just as likely to the exhaust valve, as from it. If the guide were passing oil, there would be a significant amount of oil/build-up in the port and on the stem.

Also, is that pre-cup on #3 broken? Or does it just look like it in the pic? If that is soot causing the appearance, it still doesn't look right. Bad injector, maybe? That could cause a knock. The flash pattern on the #3 piston also looks abnormal.

Good luck with it.

[john8662]

Which CDR system do you have? The one that resides on the passengers' valve cover or the one that sits above the alternator and has two tubes running to the intake. I'm gonna assume that you have the one that sits above the alternator since you're using the dual plane manifold. I've noticed on mine, since I've had the intake off a time or two lately that the oily intake ports were the middle ones. I can't say that I've seen excessive oil patterns inside the intake. But... Your engine is turbocharged, so how do you have your CDR system plumbed? Is it Banks, ATS, BAE, or Rayjay?

How much blow-by did you have with the engine up to normal operating temperature while opening the oil filler?

[78Chev]

Banks, so it goes from the right valve cover to the air filter housing. It is amazing how much oil goes from there into the air box since it then has to go through the turbo.

[78Chev]

Got the pan off. How do you check the wrist pins. Should they slide easily back and forth on the piston? What else should I look for on the bottom end?

[5.7L oldsdiesel]

The upper end of the connecting rod will slide from side to side because you have a floating wrist pin.Thats totally normal.Any traces of metal or copper filings in the oil pan?Just a little curious.

[78Chev]

Thanks 5.7LOlds. No metal that I can see. I'm draining the remnant in the pan now and will check later and let you know.

Funny that you went to 5.7 diesel. My old 78 started life as a 5.7D. Then went to an Olds gas 350 cause it bolted right up to the BOP T400. If I knew then what I know now I would have kept it and fixed it right.

[78Chev]

I got to wondering why the top of the cylinder on one side had all the carbon rubbed off on #7 while the other side (toward the back) still had carbon. All of the other cylinders have a carbon ring all the way around. So I removed the #7 piston to see if the part of the side near the top of the piston was rubbed off too. Sure enough, the portion of the piston that corresponds to the the area of the cylinder where the carbon was rubbed off matched where the piston had its carbon rubbed off. Got to playing with the rod and wrist pin. It slides back and forth normally but I can also rock it back and forth. The head of the piston is able to rock in a direction parallel to the wrist pin (90 degrees from the normal rotation of the wrist pin) allowing the top of the piston to make contact with the side of the cylinder at the top. To check this I found my old 6.2 pistons to see how much rocking motion was normal in an engine that had 170k on it. None, especially compared to the piston I just took out. So, my latest theory is that the wrist pin is indeed bad, and probably has been from the start, and that the knocking sound is probably piston slap of sorts? With the piston rocking in the cylinder the control rings might not be able to control the oil so some makes it on top of the piston?

So, if all of this is true (let me know if I'm way off here) what are my next steps? The cylinder looks good all the way down - still has good hone marks. There is a bit of scuffing that just barely goes below the top compression ring line, but I can't feel it with my fingernail. Can I have a new wrist pin installed - have the rod reconditioned, etc., etc.? What next? Please let me know what you think. I appreciate the help I'm getting here.

Randy

[john8662]

Randy,

Your theory sounds right to me, I grabbed one of the pistons out of an old 6.2 to check and see too, It's tight, it had 190k on it.

I guess the kicker here is to find out where the slack is. Is it the pin bushing in the rod, or the piston itself?

I'd go ahead and call Avant and see what they would recommend in this situation. But from my perspective, I'd recondition the rod, new pin bushing, then if necessary the new piston and rings. Lightly hone the cylinder to break the glaze and go with it.

Also, I seem to rememeber back awhile ago that you posted in the 6.5TD forum about your knock sounding very similar to the one I had recorded in an audio clip of my 6.5TD. Is this true? If so, thats certainly something I'm going to look into when tearing down that engine. I still haven't done anything with that vehicle except take the insurance off of it and park it. I don't want to tear it to pieces until I have the new engine ready to go in and just swap parts onto, don't wanna forget where things go right?

[78Chev]

I'll call Jamie and see what he says. I'm trying to figure out if the buildup on the head and piston were the cause or result or both of this situation. If the buildup was there at first and the piston made contact in that area it would definitely rock the piston in the direction of the cylinder wall where the carbon is rubbed off. But I suppose if the piston was rocking in the first place oil could have gotten by an built up in those places. The reason it is important is if it is a cause then I need to find where it came from and why it happened, and fix before reassembly. After looking at my intake manifold I'm still leaning toward the idea that oil will drain to #7 first and if the valve is open seep in there. Who knows. Anyway, I feel better about being closer to a solution.

Yeah, the noise from the recordings you made were very similar to the noises my engine was making. Everytime I'm next to a 6.2 or 6.5 I roll my window down and listen. My engine was making the noises of the normal GM diesels but with a few added knocks - sometimes intermittant; sometimes steady. After going through the lifter-changing hassle, injector swap, torque convertor checking, etc., etc., it was getting frustrating that my problem wasn't common. It was good to hear a recording of someone elses' engine just to convince myself I wasn't going nuts!

Here's a link to More Engine Pics showing the pimple on piston #5, shot of pan where oil pickup was hitting, and removed #7 piston.

[ 05-19-2005, 06:58 AM: Message edited by: 78Chev ]

[78Chev]

Well, I just checked the rod journal and bearing for #7 and they both have grooves in them down the middle. This doesn't sound good...

[78Chev]

Rod bearing pics