LLY - Cracked piston

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,761
5,933
113
Phoenix Az
you will have higher idle rail pressure due to injector size. i think i ran 6-7k on mine. 8* doesnt sound far off, you can get more timing out of a larger injector before rattling starts. my 45% overs like 12* at 500uS when cruising down the highway at 1700rpm, it was quiet as can be then (that was years ago). When i had 100% overs, i ran fingers pistons which the bowl design induces more rattle compared to a standard design so timing on both main and pilot needed work to quiet the setup down.
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
7,139
2,231
113
Norcal
I'm going to guess it's mostly related to pilot injection since it quiets down around 2200 rpm
 

NevadaLLY

Adam B
Feb 24, 2019
332
44
28
Reno, NV
Alright, we are back in business. I just towed 20k up to Oregon and back so total round trip of just over 1K miles. The build was phenomenal. No leaks, no issues, doesn't look to be burning oil. (oil change up next to double check the internals). Power was smooth and on point. I was able to pull the 7% grades at 50-60% throttle at 60-65mph. EGTS ran a bit hotter than the stock motor (might be valley turbo, might be injectors, IDK?) by about 150-200deg. So when pulling relatively flat ground, it was easy to see EGTS start to bump up to 1300 with slight inclines where I was 1100-1150 on those before. The stock Duramax is rated 1375 constant duty (i think) so I'm not too concerned there. I also towed a 7% grade in 98* weather which is over 6 miles long. About the 4 mile mark, we hit stop and go traffic so we did get some heat going on at that point, mainly trans temps. Even with the Mike L cooler (setrab), trans temps started climbing while pulling the last 2 miles going 5-10mph. It's tough to use hydraulic pressure to move that much weight for that long with little to no airflow at 98*. Just as I crested the top, trans temps were at 260. As we used trans shifting going down the back side, they briefly came up then quickly fell back to normal temps after 4-5 miles of coasting. That being a rarity, the next few passes we pulled at speed - trans temps stayed normal and TC was locked. ECT (with XDP xtra cool RAD and Xtra cool fluid) stayed around 180 (mishimoto lower temp stats) but on the long passes at 98* i did see temps come up to about 220-230 on a few short stints but never above.

I have a little work to do on tuning. But from a build perspective, I think we've made it. Thanks to everyone here who had input!

One last build question - the hot side intercooler pipe does like to "slip" a bit under the higher temps. What do you guys do to keep that baby locked down? If I clamp any more, I think I'll crack the rubber but it still slides off the turbo a bit so the pipe rubs against the hydroboost cylinder.
 

Fingers

Village Idiot
Vendor/Sponsor
Apr 1, 2008
1,717
96
48
White Oak, PA
One last build question - the hot side intercooler pipe does like to "slip" a bit under the higher temps. What do you guys do to keep that baby locked down? If I clamp any more, I think I'll crack the rubber but it still slides off the turbo a bit so the pipe rubs against the hydroboost cylinder.

Glad it worked out for you!!

I had the same thing happening at one time. I welded eyelets on the turbo and the hot pipe and put an adjustable link between them to hold that sucker together. Been that way for 15-16 years.
 

dmax_ty

Member
Aug 18, 2011
435
8
18
Utah
That’s great news man! I bet having that long trip under her belt now eases some nerves. Great job on the build. Hopefully it continues to play nice.
 

rcr1978

Active member
Apr 1, 2007
790
26
28
Spring Creek, NV
Clean the turbo an inside of the boot real good with brake clean and a rag. Go steal your wifes hairspray and put that on the turbo and ID of the boot. That worked good for me and mine was doing the same thing, Johns way is the route I was going to go if the hairspray didn't get it.
 

NevadaLLY

Adam B
Feb 24, 2019
332
44
28
Reno, NV
All, 1600mi oil change and I found a piece of metal stuck to my oil plug. Not flakes or shards, it’s a machined piece of metal…. 😳 does anyone know what it’s from? It almost looks like a dowel pin. 3F47C1D4-794A-41F7-8AAE-864DD3C0168A.jpeg
932EA3C1-5E83-4696-8C23-C2C2146CDA33.jpeg
73047147-9857-44B0-B2FF-9F9D0AEFF567.jpeg
Need advice ASAP!
 

NevadaLLY

Adam B
Feb 24, 2019
332
44
28
Reno, NV
Check the actual reluctor wheel to gear alignment pin, that Pic is the cam gear to shaft alignment pin.
That one is behind the cover, installed. I have a photo before I installed where you can see pins on top pretty well. They look too big too. Leaning on experience of all of you here to figure out what it is as I’m really scratching my head here. Could there be any turbo parts that look like this? Maybe a valve in the new 2020 oil cooler? I’m reaching here for sure42520C7B-3546-47AF-A837-5F36820B51A5.jpeg
 

NevadaLLY

Adam B
Feb 24, 2019
332
44
28
Reno, NV
You running a pinned oil pump?
Yep, pinned and shimmed. The pin on the oil pump was almost straight though. I’m leaning toward reluctor wheel. I might have a scope I can fish down through the oil feed tube to see if the cam reluctor pins are there. I don’t know why one would come out, but I think I’d be safe to run without if it did. It’s the only other pin (engine wise) I can even think of.
 

DAVe3283

Heavy & Slow
Sep 3, 2009
3,733
305
83
Boise, ID, USA
IMG_20200323_095121.jpg
There's a bypass valve in the 2020 oil cooler, but nothing that looks like the part you found.

I can't think of anything in my motor build that was a pin that small, but it is hauntingly familiar...
 
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NevadaLLY

Adam B
Feb 24, 2019
332
44
28
Reno, NV
Anyone rekeying your door locks while you where assembling the engine? Haha 😂
Lol, I wish it was simple! I have this gut feel that my reluctor on the cam is loose and about to start causing problems. I’ll get that cam in there to find out. Anyone know if you can tighten the cam reluctor bolts from the water pump hole? Would love to not take the front cover off if it comes to that. That’s if all 6 bolts are still in place. If pins are falling out, I’d guess if they are, won’t be for long. Saw another post with loose reluctor bolts and the pins were missing. I torqued that baby to spec, and checked it at least two more times before I put the cover on… but it’s the only answer I can think of.