Duramax Diesels Forum Truck of the Week
  #826  
Old 12-03-2018, 05:30 AM
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This is just my opinion but I don't think that is from the coating. Look at the ends of the rings and see if the were butting up against each other. You are missing molly in the face of the ring and the scaring looks to be something is to tight. Now I'm sure everyone is going to slam me and that's fine. BUT I have never lost a piston or hurt a motor like that. Loose is you friend. Your not driving that thing down a road or hooked to a sled for 20 seconds. That thing will see SUBSTAINED heat that most will never see. Performance engines are such fun.
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  #827  
Old 12-03-2018, 09:38 AM
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Quote:
Originally Posted by Stingpuller View Post
This is just my opinion but I don't think that is from the coating. Look at the ends of the rings and see if the were butting up against each other. You are missing molly in the face of the ring and the scaring looks to be something is to tight. Now I'm sure everyone is going to slam me and that's fine. BUT I have never lost a piston or hurt a motor like that. Loose is you friend. Your not driving that thing down a road or hooked to a sled for 20 seconds. That thing will see SUBSTAINED heat that most will never see. Performance engines are such fun.
no one should slam you! different trains of thought and if it works, it works! we dont learn if we dont look outside the box every so often.

you dont think piston coating material was transferred to the cyl wall where the rings run then they ate it? id be curious if rings that butted would still allow the piston to then hit its top side against the cyl or not. usually by the time ive seen a ring gap that was too tight, the piston was toast . just seems interesting the scarring on the piston matches so well up to the rings. maybe im not looking at it right though.
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  #828  
Old 12-03-2018, 10:00 AM
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Piston pictures are all upside down sting... LOL

I checked a couple of the top ring no sign of them touching. But I haven't pulled them off and pistons yet. From my observation, as the Piston starts up it is rocked in One Direction, coating touch the wall and rubbed off then gets caught between top and 2nd ring.

When we first got the Pistons, the TBC looked soft. So we heated one up with a torch and that coating turned very hard. Damage looks like grains of sand in that very particular area. Each piston has a matching spot on the upper and lower side of the cylinder bores. Without the coating I don't think it would have hurt being loose.

I'm driving to NC at the moment, maybe tomorrow I'll stop by with a couple for you to check out sting.

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  #829  
Old 12-04-2018, 11:16 PM
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Ok started pulling rings tonight and I can say for certain, they are not butting up or binding. Carbon on the ends, no sign of touching or anything out of the ordinary. See pic below where I scratched a ring end for contrast. With a .026 gap on top ring, and no real run time at load on engine #1, this is most revealing.

What I can say, should send Swain Tech these 16 pistons along with bill and letter from my attorney for blowing me off. Better yet, maybe I should just drive over and liquid nail these pistons to their front office window. With a note saying "reaearch adhesive properties..."

This is total BS. Shit bubbled up and started rolling UP at their tape line on land above top ring as pistons traveled downwards. Then the balled up material detached and went through the top ring as pistons traveled upwards. Pieces of it on top and behind second ring on 2 of the 3 sets I've pulled so far. Some damage to the piston lands also.

What's more interesting, most of the damage on this engine is near exhaust valves. Not seeing any on the intake side of this one due to low hours. So the whole PTW question is also useless. Only issue is their junk ass TBC that I questioned from day one. See how thick it was applied.

Fingers, call Mike over there and tell him your customer has a caulking gun and is headed to a hardware store.. Need 2 sets of new rings minimum, and likely 5 or 6 pistons to make it right. And I haven't even honed the block'S yet.

BS BS BS...

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  #830  
Old 12-05-2018, 04:49 AM
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Going to Burket racing?
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  #831  
Old 12-05-2018, 06:04 AM
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So yours were coated on the sides down to the top ring-land?
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  #832  
Old 12-05-2018, 10:39 AM
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Originally Posted by rcr1978 View Post
So yours were coated on the sides down to the top ring-land?
Yeah coated only about halfway down. This call also on the suggestion of swain to protect the crown. Zoom in on piston pic post 783.

NC, I ran down to Raleigh to check out an LT5 engine my buddy at Crawford Racing is doing. Little CANBUS and L5P throttle body hacking side project.

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  #833  
Old 12-05-2018, 11:06 AM
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Yup just seen the pic, wonder if it would have done as much damage if just the tops were done?
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  #834  
Old 12-05-2018, 12:09 PM
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No, from what I can tell the worst of it is related to the side coating. However on the other engine there is some scratches that don't Mach up. And flaking off the top is surely gonna cause hot spots where it's missing.

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  #835  
Old 12-05-2018, 11:38 PM
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On engine #1, 7 of 8 top rings show significant damage on the face. Mostly isolated to area matching the coating damage on top land. Being the short run time, the rings don't look to have rotated much from installed positions.

Only a couple of the second rings showed any marks where material passed them. However I found what looks to be some lost TBC on top and behind the second ring.

See comparison of the one good top ring to another where TBC was in bad shape. Last is pics of a second ring before wiped down to show the gritty left overs I found.

Open to alternative theories if anyone has something better to explain it.



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  #836  
Old 12-05-2018, 11:42 PM
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On a good note, the pressurized wrist pin bushings look to be running happy happy happy on both engines..



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  #837  
Old 12-05-2018, 11:59 PM
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Here is a PDF I found that examines many types of diesel piston damage, and offers known causes with detailed explanations.

Good read, with pictures..

https://cdn2.ms-motorservice.com/fil...ying_51730.pdf


Mine seem to be closest to example #42.
  • Pistons with an incorrectly shaped bowl or an incorrect bowl depth or diameter.

Now that is funny...

Last edited by kidturbo; 12-06-2018 at 12:06 AM.
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  #838  
Old 12-06-2018, 12:28 AM
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I'm no expert in this area but it looks a little more like #22 to me
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  #839  
Old 12-06-2018, 10:15 AM
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I'm gonna have to go with 42 also, there was similar wear on Brett Duestch's pistons he was selling used, never saw the bores though just the piston pics. It appeared to me the injector spray area on the outer oval caused a hot spot due to the smaller amount of material there so there was more expansion in that area. It's been a while since I looked at those but I thought his marks lined up roughly with the injector spray pattern. I think the coating on yours made it worse since it closes the clearance even more.

I'm not dead set on this it's just a theory on my end and it's in no way of a no insult to John on his pistons, now would I rather have a few piston scuffs instead of a cracked piston and ruined cylinder yeah so you loose in a few areas to gain in others. Big injector pulse surely makes the problem worse, guys with huge injectors and smaller pulse width's with these pistons probably never see anything on the pistons.
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Last edited by rcr1978; 12-06-2018 at 10:33 AM. Reason: ill speller
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  #840  
Old 12-06-2018, 12:17 PM
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Quote:
Originally Posted by rcr1978 View Post
I'm not dead set on this it's just a theory on my end and it's in no way of a no insult to John on his pistons, now would I rather have a few piston scuffs instead of a cracked piston and ruined cylinder yeah so you loose in a few areas to gain in others. Big injector pulse surely makes the problem worse, guys with huge injectors and smaller pulse width's with these pistons probably never see anything on the pistons.
Yeah I'm gonna say while this set only made a few short pulls, they saw the biggest pulse width [2850us], most heat [1800f], with shortest break in period [has oil pressure, send it] ...

Which all those points alone fall under several possible causes listed in that PDF. If you read each description matching where these show contact, none are definitive. Plus these piston tops were shaved an additional .010 to match block deck work. So it's totally possible they are deforming slightly, or oil film was getting washed down with fuel, allowing coating to touch the wall.

And while you won't find a picture anywhere, nor did Jon receive it back, I have seen a cracked "coated" oval bowl with my own eyes. The crack went right across the top half of the oval cut, not centered over wrist pin as is most common. So the weakest point has obviously moved with his design mod.

But how does all this play into the coating issue? To me, it doesn't change fact the coating is what damaged the rings and mauled the cyl walls. If we had started out with bigger injectors as switching to now would it still occurred, most likely yes. If they had only coated the tops and not over the edge, then some of the missing chips in set # 2 would likely have still made their way down into the rings. That I believe true. So TBC is still bad... MMKAY!!

The gold coating seems to be applied thinner, and adheres better than this TBC. I've spoke to several builders running on forged pistons in gas engines and none report any such issues. I can't find anyone who has used the TBC, but recall someone posting a pic on here from years back showing it cracked and lifted also. Maybe I'll do a search when have time.

Last edited by kidturbo; 12-06-2018 at 01:00 PM.
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