Built Motor Reliability

[duramaxdiesel]

I don't know about you guys but I'm starting to freak out here! Many built motors are blowing up. I guess the DPC was running and seeing the carnage there doesn't help. But even regular members aren't even making it to 25k before they go BOOM! Why is this happening? Isn't the purpose of a "built" motor for it to stay together? I'm putting a HUGE amount of coin in my motor and have used all the brand names from Guy at SoCal to the turbos that will be coming from Brayden at Fleece Performance. But so are others and they still blow up.

What are your guys' thoughts??

Nick

 

[gmduramax]

Built motor just means the parts are strong enough to hold big power, for how long depends alot on the machine shop and parts used.

 

[ripmf666]

I have around 47,000 miles on my build this July will be 3 years. The LB7 we built has well over 70k in 2 years on it.Its all in how clean everything was when it was built and the machine work was right. I have beat on my truck but the LB7 gets beat on almost everyday and harder on the weekends.

 

[Rhall]

I think theres a lot more to play than machine shop. A machine shop will have nothing to do with wether you loose a piston or not. Broken cranks seem to have nothing to do with that either since if seen them break out of a lot of shops while another one out of the same shop will last forever. When you get up in the 900hp+ range you are just at high risk no matter what, nothings bulletproof, drag racing is def harder on motors than sled pulling, tuning and good injectors also play a role in piston life. My cut, uncoated cast pistons are on their 3rd season, i will go forged next time, but mainly just because the size of valve reliefs i want to put in.

 

[Stingpuller]

Built motors

My shortblock has been together since 2009. At that time I changed the pistons but not because they were hurt. I changed them because they were made wrong. They put the valve reliefs in the wrong spots. The rings were the only thing that needed chaged since it was orginal from 08. The bearings and everything are still the same. RHall said it best when the power goes up the life goes down. It doesn't matter who builds! I still think a good machine shop that understands big power is a big plus. When you jack the power up things need to be done different than a stock rebuild. It's really hard to expect a long life out of anything when your asking it to handle 3 times the power it was made to take. Jeff

 

[GMC_2002_Dmax]

Tuning plays a big parts as well as how you drive it and who assembled it.

I have many customers that have been running fine for many miles and some that break stuff all the time.

Usually when it breaks it is the crank shaft. That is why IMHO if you are spending serious coin to build a motor the Stroker Kit from SoCal Diesel is worth the extra few $$$

 

[Rhall]

Tuning plays a big parts as well as how you drive it and who assembled it.

I have many customers that have been running fine for many miles and some that break stuff all the time.

Usually when it breaks it is the crank shaft. That is why IMHO if you are spending serious coin to build a motor the Stroker Kit from SoCal Diesel is worth the extra few $$$

What about the stroker kits that have broke cranks? Is there enough running to prove that they will hold up better? I know they havent proven more power yet... And i would also say, while crank breakage happens with these, pistons are more common.

 

[Akdiesel]

Just a question from a newb but doesn't internally balancing a crank make sense? I know that it is possible and don't see why the diesel world doesn't utilize it more often. I know shops have used it and I've yet to hear one of their internally balanced cranks break

I would think it's pretty easily understandable that an externally balanced crank is not a truly balanced unit front snout to ass end and unless it's balanced with proper weight (simulating the weight of the rod/piston combo) it's not really balanced at all and will flex or bow in the middle (ie where all dmax cranks break at the #2 rod journal)

Feel free to flame away and tell me I'm wrong

 

[duramaxdiesel]

Just curious, but how much more would a internally balanced crank cost? I never even thought of that when I did mine.

Nick

 

[paint94979]

Anything above 700hp seems to be nobody knows threshold...

 

[Akdiesel]

Have people been breaking internally balanced cranks?

 

[blk smoke lb7]

I dont know but i also am worried about my motor,in the machine shop now and getting built,i did request for rotating assem to be ballenced before installation so i hope this will help and ati ballencer will help as well im sure

 

[McRat]

Have people been breaking internally balanced cranks?

I supposed to test an internally balanced SoCal stroker crank in the future at some point.

We didn't break our SoCal externally balanced stroker crank.

If my reading is correct, 2 of the Diesel Power Challenge trucks were running SoCal internally balanced cranks, not sure if they were strokers or not.

 

[Akdiesel]

That's good to see that people are using them. I just couldn't imagine a $15-20k motor with a stock crank and reusing stock pistons just to see it break again and be at square 1....but I guess I'm cheap and don't make enough money to piss it away like that lol

 

[Rhall]

That's good to see that people are using them. I just couldn't imagine a $15-20k motor with a stock crank and reusing stock pistons just to see it break again and be at square 1....but I guess I'm cheap and don't make enough money to piss it away like that lol

If you use a stock crank, and stock pistons, you shouldnt have near that much in it. If you break a billet crank (which has been done more than once) your still back at square 1, but you have a lot more in it. Some forged pistons dont have a good track record either. You melt or crack one of them, your still back at square one. It really doesnt matter how, who, or what parts you have in it. If you want to make big power, its a gamble. Im glad to see people are starting to do internal balancing, i know of a few pullers doing it this year, one of them a stroker crank, im interested to see how it holds up. I know Kusileks did it with one of their motors last season... not sure how it held up, i think they faught a lot of stuff all year.

 

[TrentNell]

If it is harmoics breaking cranks why did my un balanced engine not break the crank last year @ almost 1200 HP ? This is not a jab just pure curiosity and thinking out loud , I know engines from a mechanical since very well but know little about harmoics , engineering, ect .

On the second note , short of piston failure I think the rest of the Duramax engine is fairing pretty well for holding big power , and common since will take you along ways .

 

[McRat]

I've never broke a crank and have used both LLY and LBZ cranks.

But I've seen stock and nearly stock trucks break them.

I think this is similar to the LBZ/LMM piston. There is a certain percentage of factory defects that don't show up on the test stand.

 

[juddski88]

From talking with EDP and also another member here, internally balanced cranks have not proven to increase crank or bearing life, and have also shown in some cases not to run as well as an identical externally balanced crank. I was all for it until I started gathering info...

 

[Stingpuller]

Balance

Mine is external but it was done by one of the best machine shops in the nation! I think it matters. Mine might break the next time out but so far it has hold up pretty good. Many may not agree but untill these motors start turning higher rpm's I personally don't think there's a lot of differance. Now if the rpm's go higher then I believe it will matter. I was at Brayden's before they went to the dpc and checked out Owen's truck. Sorry Owen I was really hoping you guy's would kick butt!! It can't hurt to internally balance a motor and might help but I think it's just more of a power pulse on the crank that breaks them. Piston's is a whole nother problem. You can cut them, coat them even bless them but stock piston's are still stock pistons. A cast piston was never intended to deal with the pressure it takes to make big power. I think (fwtw) that Mahle uses the wrong aluminum in there pistons. They run a high silicon content to try and get a bunch of miles out of them but it makes them brittle. Much like a hyper piston with high silicon. They don't like detenation or rattleing the rings. Run the softer aluminum with a little more clearance and they will last longer with big power. Everyone needs to remember that nothing will last forever. If you turn the wick up the life will go down. These trucks a heavy and load a motor in a different way than what most other motors see. Jeff

 

[McRat]

I think we need to look at the Audi roadracing program to get a glimpse into our future.

They had to switch to steel pistons (Mahle), and they spin to about 5500rpm IIRC.

If Audi could have made the alum pistons last for a 24hr race, they would have. And they if they could have spun faster to make power, they could have reduced engine and transmission weight (less torque means lighter pieces).

They are using special fuel, and are smaller piston disp, so 5500rpm is probably not realistic for us. 5000rpm should be about our max sweet spot, if not lower. A GT45 will make peak at 4800 with our engines btw. It will make about 800rwhp uncorrected even with stock injectors up there on pump fuel. In theory at least, a well-set-up GT45 truck on fuel can use stock LBZ+ rods even with steel pistons and be a fairly reliable and cost-effective combo. The GT45 I tested was a PPE GT42 Magnum, which is a GT45 that bolts in where a GT42 does.