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Discussion Starter #1
About a year ago I deleloped what sounded like a valve tap. I used a stethoscope and traced it to #3. After about 6 months the tap went away on its own. After a few months it returned, as more of a clatter. The tap rate is half the rpm so it's upper end, not lower, for sure.

The clatter is intermittent. It clatters, then it doesn't, then it does. Sometimes I notice a miss, then the miss disappears. The clatter has largely subsided, but now I notice when I press the pedal to the floor, (I'm presently bobtailing) I get a continuous stream of dark grey smoke from the stack. This is new. The engine always smoked, some, but never put out a long continuous trail on hard pull like it's doing now.

Malfunctioning injector?
 

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Better check your roller lifters. I lost one once and it was a mess fixing everything. New cam, blah, blah$$$$$. Could be an injector possibly. Check your dowels that the bridges ride on. I have heard of them coming loose. Also heard of broken valve springs and stuck rotators. Probably not a lifter , but any time someone mentions half of crank speed that is what pops in my head instantly. It made a noticeable clicking sound for about 800 miles (that I drove it, had a driver in before that) before it came completely apart and knocked lobe off cam. Get a svc manual off ebay if you don't have one and replace the anti-rotation clips on the lifters and check the lifters over real good per the service manual. If you don't have to replace any lifters you should be out less than 250 bucks for book and parts. If a lifter comes apart figure 3500-5k if you do the work. Cat says to replace the ar clips and inspect lifters anytime head is off or iirc around 600k miles. Nobody much seems to do it though. Mine came apart at 1.3mil. It missed and smoked raw fuel when that happened. Sounded like driving with Jake stuck on on 1cyl. Could be a bad injector or related causing the smoke or even the timing advance.I have never heard injectors make any unusual noises on an 06 when failing but timing advance can- usually right before it grenades. Advance would be half speed but if you used stethoscope that kinda puts that to the back of the line. You may have two separate issues. need more info to speculate on smoke very much. Has your boost or pyro changed any and such.
 

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Discussion Starter #3
Thanks, w91, that's informative, and it sounds like good advice.

I do have a manual for the engine. It is at home and I am on the road. I'll be heading home soon and I'll dig it out.

This engine never ceases to amaze me with its good performance, knock on wood. It has stopped making any noise and it has ceased spewing excessive smoke. I'm baffled, but I'm not complaining. I don't know what happened, but I will check the lifters and replace the anti rotation clips.

There is no question that the loudest, by far, noise coming through the stethoscope was when I put it right to the front valve cover at number 3 position. It's gone now. Again, I can't figure it for the life of me.

What to do at this point? Get my manual and check things out like you suggested.

Thanks again.
 

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I’d be my paycheck that’s a injector failing. I’m dealing with that now on a big cam cummins. The tapping noise would come and go on mine. You want to address it ASAP, because it can lead to much bigger problems. And if I remember correctly (it’s been a while since I messed a a b model cat) those pencil injectors are fairly cheap. Good luck to ya, and I’m curious as to what may of been the problem if you already figured it out.
 

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I’d be my paycheck that’s a injector failing. I’m dealing with that now on a big cam cummins. The tapping noise would come and go on mine. You want to address it ASAP, because it can lead to much bigger problems. And if I remember correctly (it’s been a while since I messed a a b model cat) those pencil injectors are fairly cheap. Good luck to ya, and I’m curious as to what may of been the problem if you already figured it out.
Curious too.:popcorn
 

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Discussion Starter #7
I’d be my paycheck that’s a injector failing. I’m dealing with that now on a big cam cummins. The tapping noise would come and go on mine. You want to address it ASAP, because it can lead to much bigger problems. And if I remember correctly (it’s been a while since I messed a a b model cat) those pencil injectors are fairly cheap. Good luck to ya, and I’m curious as to what may of been the problem if you already figured it out.
I was on my way home with it. It gave out on I81 in PA. It started making a deep noise that I thought was a rod knock, but it wasn't. The engine wasn't throwing smoke and it seemed to be holding speed alright. Oil pressure was all the way up. I stopped in the TA in Greencastle and opened the hood. I had a lot of blowby coming out of the breather and the dipstick tube. I called a tow truck. I finally got around to opening the valve cover and lifting the Jake brake.

It's number 3 like I thought. The injector broke through the retainer cap. The exhaust valve to the passenger side is pushed up. The rocker came off the exhaust valves and the pushrod must have fallen into the crankcase.

I'm going to pull the head, but first I need to get my Detroit running. Things don't look good for me right now.

What could drive an exhaust valve up 1/2" higher than all the other valves? The keepers are missing. The only thing there is the valve stem, sticking up all by itself, 1/2" higher than all the others. The other cylinder 3 exhaust valve looks like it's alright.

My Detroit has oil in the coolant, no coolant in the oil. I think it's been doing that for a long time. It's been sitting 4 years. I'm wanting to run it now, but I don't know how serious a problem I have with oil in the coolant. When I'm idling with the pressure cap loose, coolant drips out, then stops for a few minutes, then drips for a few minutes then stops again...
 

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Sounds like the head of the exhaust valve broke off. Most likely the extra piece inside the cylinder pushed up on the injector tip breaking the retaining cap. Lots of damage to that cylinder for sure. You will need to check the exhaust side of your turbo for damage also.
 
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