Failure Brainstorm/Brainfart

[DaJokr]

I really didn't know what to call this thread, but I'm hoping some of you very knowledgeable guys can contribute and help me understand...because I'm honestly not the sharpest tool in the shed.

A thread popped up on another forum about the fastest stock bottom end duramax to run a 1/4. While I'm interested in finding out the time, I'm more interested in figuring out the whys of particular failures.

Let me start by stating the facts as I understand them. I appreciate any clarification here as I truely wish to understand my truck better, so that when I finally am able to sink some serious money into this hobby I have come to enjoy, I can make informed decisions and have an idea of logical progression. Also as I own an lbz, I will be implying what I know about that platform. I know the lb7 to lmm are similar, but the lml i currently don't know that much about.

Egts are the devil, I think this was the first thing I understood when I started looking at diesels. I'm not sure at what temperatures to avoid, but being I have seen 1800+ I know I am definitely out of the green and deep in the red. Therefore a key to making power and preventing failure would be egt management. Please correct me if I'm wrong folks.

Pistons and rods. Pistons are crap compared to the lb7/lly but rods are improved. Lbz/lmm use the same pistons and rods. Piston failure is common, seems heat related, boost no doubt is a contributing failure. That said the wrist pins (?) are a weak point due to the lack of material on the piston, but was there another part to this I'm missing? What all contributes to cracks and holes?

The con rods themselves while stronger then previous generations are prone to bend/break at higher hp levels. Everything I have read though they seem to let go around the same power levels as the earlier versions, so I don't understand how they can be considered improved. I understand pressure causes this, but is it the hp or torque? Upper or lower rpms? How can you push power and reduce stress on the rods?

Cranks are hit and miss, they either break or they don't. Stock power to high power. Was trying to figure out why, looked through the thread fingers posted, reread more then a few times. From what I understand, it has to do with the firing order of the pistons which is why people run AF cams, to change the firing pattern and reduce pressure on the crank.

What other areas are prone to destruction? If a person wanted to test the limits as safely as possible (for testing purposes, I realize your playing with fire) where would you start? I'm all about seeing what I can do and push one upgrade at a time. That said my truck is no spring chicken, I realize it could break at any point, but I'm still willing to test theories in the pursuit of knowledge.

Right now I was planning air flow mods:

Exhaust
Dp
Manifolds
Up pipes
Intercooler boost tubes
Y-bridge

What are your thoughts/ideas? I'm letting myself be a mule here so if anyone has ideas or theories and are looking for someone dumb enough to try.

I'm all ears here guys/gals, educate me and help me push the boundaries of what is the usually accepted on the road to a built motor.

 

[Harbin_22]

Ryan Funk went [email protected] with a stock engine LBZ. Single 75/83/.90, 60% Inj, 2 stock pumps and a little spray. ECSB weighing in around 62-6300#'s. He went multiple 6.90's and ended up with a blown head gasket after years of beating on it. Mine went 11.6@119 at 66-6,700#'s and shit a rod out of the block shortly after, but I had small twins that made alot of power down low.

 

[DaJokr]

That's hella fast. I'm trying to do that with a 7-7100 pound ccsb. Shall have to see how much I can gut it down the road.

See my theory is it's a combination of heat and pressure that causes the breaks. If you can keep temperatures low and build pressure at a constant rate, I would think this would help prevent breaking/bending parts. I always thought the hit from a big single when it lights would create a lot more pressure then a twin setup since twins are a more consistent flow of power from the bottom to top, whereas a big single is mid to top if not just top. Twins keep egts lower but have the inherent downside of increased back pressure, not sure whether that effects the internals or is just a problem for the turbo though. More clarification is needed in this area. I know tuning will be key.

 

[Harbin_22]

That's hella fast. I'm trying to do that with a 7-7100 pound ccsb. Shall have to see how much I can gut it down the road.

See my theory is it's a combination of heat and pressure that causes the breaks. If you can keep temperatures low and build pressure at a constant rate, I would think this would help prevent breaking/bending parts. I always thought the hit from a big single when it lights would create a lot more pressure then a twin setup since twins are a more consistent flow of power from the bottom to top, whereas a big single is mid to top if not just top. Twins keep egts lower but have the inherent downside of increased back pressure, not sure whether that effects the internals or is just a problem for the turbo though. More clarification is needed in this area. I know tuning will be key.

In my experience, twins drop drive pressure since it keeps both turbos in their efficiency range

 

[DaJokr]

Mind explaining drive pressure and what it affects?

 

[TheBac]

Look up Camomax.

And you should seriously consider reducing the vehicle weight as much as you can when you run. Why leave hp on the table by carrying unnecessary baggage?

 

[DaJokr]

The plan is to either strip this truck down and cage it or if I find a rcsb roller for a decent price move all my upgrades over to it. But that is besides the point here as I know I need to loose weight and am already taking steps to drop this. I. Trying to hit 12's with just a trans and a tune currently, weight and elevation are fighting me though.

I still need to understand my inner workings better. I could throw parts willy nilly like the majority of people do, but I prefer to do my research and actually understand now. Make informed decisions and understand what I'm doing and hopefully teach others in the process. I've started googling back pressure, and I need to look more into turbo a/r as it still doesn't make sense. I will look for camomax, thanks for the suggestion.

 

[TowU4Free]

Subbed here as in in the danger zone with my setup but still have to bug to go faster !

 

[Awenta]

Keeping the power up high will help it live.

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[TheBac]

100% of all what you guys are talking about has been discussed on this forum in the past. Its essentially all the same stuff we were talking about when I was trying to run low 12s and when Trent was building his truck.

 

[JoshH]

As far as I know, Camomax has gone the fastest with a stock bottom end. I think it was in the very low 10s if I remember correctly, but it didn't last very long.

 

[hondarider552]

My stock engine lb7 single cab didn't even make it to the track with a stock engine, 75mm and spray :roflmao:

 

[andy-stevenson]

I'd be really curious to see what effect if any an AF cam would have on a stock internal motor.

 

[Awenta]

Has to be done with a new crank to be a good comparison

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[DaJokr]

Has to be done with a new crank to be a good comparison

Sent from my SM-N910V using Tapatalk

Agreed, and I'm more interested in finding ways to make the stock components work better anyways.

TheBak, I'm looking for your 12 second build. I'm assuming I will have to dig through build threads to find the info. I'm aware there is info scattered all over the forums on these topics, I apologize if you find it annoying. However, they are just that, scattered. It would be nice to have everything easier to find for those who haven't been around these forums as long as you. I'm doing my best to find threads and will post links to the ones that may pertain to the idea behind my thread to maybe avoid these nuisance threads which contain info that has been talked about a million times before.

 

[CarolinaHD]

Just go to Tom's profile and search his started threads, it'll be much easier that way

 

[Hot COCOAL]

I'd be really curious to see what effect if any an AF cam would have on a stock internal motor.

I believe Jon (Fingers) has data charts/data analysis (and how I understand it, is) showing how the firing order of the stock cam creates a harmonic resonance which is "believed" to actually resonate at a freauency that affects the structural integrity of the metal/iron in the crank...

The firing order of the AF cam is supposed to reduce that resonance/frequency created by the stock firing order cam, which in turn is supposed to reduce "harmonic stress" on the crank...

IIRC, in talking to Mark B, he has said that you can actually feel some of the stock cam trucks shake the dyno, whereas the AF cam trucks never do...

 

[andy-stevenson]

I believe Jon (Fingers) has data charts/data analysis (and how I understand it, is) showing how the firing order of the stock cam creates a harmonic resonance which is "believed" to actually resonate at a freauency that affects the structural integrity of the metal/iron in the crank...

The firing order of the AF cam is supposed to reduce that resonance/frequency created by the stock firing order cam, which in turn is supposed to reduce "harmonic stress" on the crank...

IIRC, in talking to Mark B, he has said that you can actually feel some of the stock cam trucks shake the dyno, whereas the AF cam trucks never do...

I was wondering if the AF cam and harmonics and resonance would play any part in helping rods stay straight?

 

[DaJokr]

I'll dig through toms threads some more.

I remember reading about that in fingers thread. When I get back to reading it I will most likely post a link in my original post linking it. Seems like a straight forward simplification of what he said though. Thanks for adding Jason.

 

[Hot COCOAL]

I was wondering if the AF cam and harmonics and resonance would play any part in helping rods stay straight?

Not likely... I couldn't say fer sure, but I doubt it because the cam (in a stock type grind) isn't gonna bleed off Cylinder pressure, so the CP at quench/ignition is still gonna carry the same potential...

Using the AF cam reduces the harmonic frequencies, but all the parts still recieve the same forces as before, parts still get the same heat, inertial forces and pressure and the metal itself can only take so much force before the metal gives and you blow holes in pistons and bend rods...

Just my thought, could be wrong...usually am :hello: