Competition Duramax Cracks

[Yo Hoot]

I am of the opinion that the DuraMax block in the picture failed ,not because of a weakness in the block , but as a secondary event, to a rod failure. The rods in this motor are fairly strong to the failure point , the failure point is also related to the tune up.



As in any other form of motor sports when you break a part, you do a post failure analysis and extrapolate the primary cause of the failure and any other contributing factors. The primary cause of DuraMax failures are rods integrity and crankshaft flex. These failures become more apparent and exaggerated in lower RPM from over unit loading of these parts . as RPM goes up the ability of the engine to produce these loads need to cause failure of parts goes down . and from this we learn that if we can raise the RPM that we make peak power we can make these parts live at a higher HP level . this goes hand in hand with making more usable HP .



In the motor sports engineering community there is only one way to produce more useable power , whether its in a Indy car , NHRA stocker or a diesel drag racing engine , that is to burn more fuel with the proper corresponding amount of air. There are two ways to achieve this , first make the physically motor bigger , or trick it in to thinking its bigger . that is make it have more actual displacement or make it think its bigger by artificially raising the pressure in the intake track above atmospheric. So there we have it , more CID or more boost.

Second is to make it have more power pulses , there by burning more air and fuel or in simple terms turn it more RPMs and this in my opinion is the only answer to making power and not breaking parts.





Now how to achieve this ,

Improve cylinder fill , this is achieved with better cylinder head intake track , and camshaft design. If you have less restriction thru the intake track , and the cam works in conjunction with the heads air flow map. then you turbo can move more CFM of air in the sweet spot on the turbo’s map. Now that you have air flow you can rev the motor up , creating more power pulses per minute and thereby making more total power. The RPM this is achieved is well over the torque peak and provides less stress of the weak links in the motor.



The DuraMax has many advantage over the other motors such as big journal cam cores , 60 mm and very stable valve train. This allows the valve to be controlled in a more precise way achieving maximum window to flow air through , and not have long seat timing that hinders cylinder pressure issues the heads on the DuraMax are in max ported form approximately 75% better in air flow then the Cummins aside from being a 125 lbs lighter.

All true except.....



Inside sources tell us GM/Isuzu knows of the weak block, have failed countless blocks in durability testing and have redesigned the block to handle the increase in stock hp to 360.

 

[Marco]

To COMP461's thought's, I'd like to add that the D-MAX PCM's are amazingly simple to tweak for more RPM's. Took me very little to find out how to do it.



More than that, the D-Max engine DOES produce power above 4K Rpm in stock form. Only a little PCM tweaking, voilà.



What I don't know is how long the engines will last..... :-laf



Marco

 

[Yo Hoot]

To COMP461's thought's, I'd like to add that the D-MAX PCM's are amazingly simple to tweak for more RPM's. Took me very little to find out how to do it.



More than that, the D-Max engine DOES produce power above 4K Rpm in stock form. Only a little PCM tweaking, voilà.



What I don't know is how long the engines will last..... :-laf



Marco

You do now

 

[KBennett]

I am of the opinion that the DuraMax block in the picture failed ,not because of a weakness in the block , but as a secondary event, to a rod failure. The rods in this motor are fairly strong to the failure point , the failure point is also related to the tune up.



As in any other form of motor sports when you break a part, you do a post failure analysis and extrapolate the primary cause of the failure and any other contributing factors. The primary cause of DuraMax failures are rods integrity and crankshaft flex. These failures become more apparent and exaggerated in lower RPM from over unit loading of these parts . as RPM goes up the ability of the engine to produce these loads need to cause failure of parts goes down . and from this we learn that if we can raise the RPM that we make peak power we can make these parts live at a higher HP level . this goes hand in hand with making more usable HP .



In the motor sports engineering community there is only one way to produce more useable power , whether its in a Indy car , NHRA stocker or a diesel drag racing engine , that is to burn more fuel with the proper corresponding amount of air. There are two ways to achieve this , first make the physically motor bigger , or trick it in to thinking its bigger . that is make it have more actual displacement or make it think its bigger by artificially raising the pressure in the intake track above atmospheric. So there we have it , more CID or more boost.

Second is to make it have more power pulses , there by burning more air and fuel or in simple terms turn it more RPMs and this in my opinion is the only answer to making power and not breaking parts.





Now how to achieve this ,

Improve cylinder fill , this is achieved with better cylinder head intake track , and camshaft design. If you have less restriction thru the intake track , and the cam works in conjunction with the heads air flow map. then you turbo can move more CFM of air in the sweet spot on the turbo’s map. Now that you have air flow you can rev the motor up , creating more power pulses per minute and thereby making more total power. The RPM this is achieved is well over the torque peak and provides less stress of the weak links in the motor.



The DuraMax has many advantage over the other motors such as big journal cam cores , 60 mm and very stable valve train. This allows the valve to be controlled in a more precise way achieving maximum window to flow air through , and not have long seat timing that hinders cylinder pressure issues the heads on the DuraMax are in max ported form approximately 75% better in air flow then the Cummins aside from being a 125 lbs lighter.

Comp, did you really write this? Your spelling and grammar sure has improved

 

[Amish Elegance]

What about lubrication at those rpms? Looks like those cam bearings were pretty well gone.



(lubrication) May be one of those support upgrades needed for bigger revs on the d-max.

 

[Marco]

Now that you mention the lubrication. On the engine test bead one thing I noticed was that the D-MAX oil temps did run always awfully hot. At least 45-50° hotter than the Cummins. Hmmmm... .



Marco

 

[RacinDuallie]

Comp, did you really write this? Your spelling and grammar sure has improved

Whatta ya expect from a chivvy racer? He used to race for G. M. perfomance parts... .

Get them chivvy boys talking Mopar and they get all tongue tied:-laf :-laf

 

[Turbo Thom]

I'm gonna tell y'all right now, you keep on picking on the duro's and you will have Greg going over to the DieselPlace. Now do you really want that? :{

 

[biggy238]

The lubrication aspect was why I spit out the gun drilling the block comment.



Unfortunately I don't have a racing or engineering background to base my comments from, but isn't it the least bit counterintuitive to state that higher RPMs are the saving grace of a motor?? I mean, after all, one of the things attributed to the longevity of the cummins is the fact that they never see legitimately high RPMs.

And something makes me thing that those duramax block failures aren't happening within factory spec rpm bands. Could just be me though.

Overspin it, blow the rods apart and then blame it on the lack of rpm??? I'm justa simpleton. .

I don't like your rods but you've got really nice heads... .

 

[COMP461]

The oiling system of the Duramax is a priority main system, and is not really the problem if you clearance the bearings properly. I did a trial assembly of my newest racing Cummins, and with a 55 motor home block that Cummins greater south west donated to the cause and coated Cleveite 77 bearings, with my tried and true lighten race crank the oil clearance was 1 and 4 tenths thousands. This was out of the box parts and way to tight for a race motor, but would have run a million miles in a stocker motor home. The Duramax is the same way way to tight for racing, the cam is no problem in the Duramax if you will roller bearing it , the Cummins responds very well to roller bearings I have moved from the Cummins 54 mm cam to a 60 mm cam with the rollers .



The reason behind turning the motor harder is to not place the loads the torque will make at lower Rpms , the Duramax rotation assembly is good to about 7500 Rpms if you could turn it that hard , but that is not a possibility with current fuels . Or the head air flow. Remember that RPMS are just a number and to not be scared to rev something up , the real killer is unit loading of the motor down low



Example 600 hp at 1800 rpms is 1750 foot pounds of torque



600 hp at 2600 rpms is 1200 foot pounds of torque



600 hp at 4000 rpms is 787 foot pounds of torque



or as in my trailblazer motor



600 hp at 8800 is only 358 foot pounds of torque



All four motor make the same power and if you had the right gearing and the motors could accelerate in rpms per second corresponding the gear ratio then you could make all run just as fast ,



But the laws of physics are still in play so several things are apparent



1 the low rpm motors break things both motors part and drive line parts.



2 the low rpm motors will not accelerate and still make power. Meaning at 600 to 900 rpms per second acceleration rate they fall on there face. The higher the rpm the less you proportionally need to accelerate it; you put a loose converter in it and let it do all the work.

 

[Battering Ram]

Keep thinking that about the G. M. Duramax , the reason most of these fail, is unit loading from running the engine at too low a RPM and not using the incredible breathing ability of the heads. This motor will be the one to beat in the near future. With head flow in the 325 CFM and the fact that there is 4 more intake valves the total CFM per CID is about 50% greater in addition to having 35 more of them . I’ve seen a Duramax a 800 + hp on a super flow 901 this was on diesel only . this motor was built for endurance racing so , there is a lot left in the mix

Now this engine doesn't just happen to be in Azusa California does it? That Duramax isn't sporting a race prepped Bosch EDC16 ECU along with a CP3. 4 fuel pump that just so happens to flow about %66 more fuel than the CP3's that are on the Durmax and Cummins? Wish I could get Bosch to ship me two Common Rail fuel pumps that are not sold in the US so I could play with them. Wonder how much power a Common Rail Cummins could make with a fuel pump that big with the amount of boost it can handle... doubt the Cummins would fit very nicely in a truck designed for the NASA roadracing circuit though.



Horace

 

[COMP461]

some of it right , some of it wrong ,



the new long block we received yester day is a LLZ and is improved in the main .

 

[Yo Hoot]

some of it right , some of it wrong ,



the new long block we received yester day is a LLZ and is improved in the main .

You mean LBZ?

 

[Dakotahaulers]

I have watched a 730 Hp Duramax stay together for at least two years now. The same truck that beat Jim's 12v. He has driven it daily to work about 70-75 miles one way. The truck just blows my mine on the track and on the dyno and is his only pickup. When I first seen the truck perform it had a utility bed on it. I think he is around the 70,000 mile mark.

 

[Yo Hoot]

They are tough but most likely he didn't have it hit 730 hp early in it's life. Also no one runs that hp around town.

 

[RacinDuallie]

NO ONE RUNS THAT HP AROUND TOWN.



Yo Hoot,
Oh no? Well maybe not around in YOUR town:{ ... ..... There are lots of us rolling around with sleeper cars - and trucks for that matter ... ... I'm building a KILLER '64 Fury- 4 door no less!:-laf Plain Jane looking too... ... heh heh heh..... very soon equipped with a date coded '64 Stage 3 Max Wedge ... .




Oo. Pinks anyone?

 

[Yo Hoot]

NO ONE RUNS THAT HP AROUND TOWN.







Yo Hoot,

Oh no? Well maybe not around in YOUR town:{ ... ..... There are lots of us rolling around with sleeper cars - and trucks for that matter ... ... I'm building a KILLER '64 Fury- 4 door no less!:-laf Plain Jane looking too... ... heh heh heh..... very soon equipped with a date coded '64 Stage 3 Max Wedge ... .









Oo. Pinks anyone?

No I mean just because your vehicle is capable of 10,000 horsepower doesn't mean when using it every day you are using that power.



When someone says I have 740 hp and I use it everyday for 70,000 miles I call that BS.

 

[RacinDuallie]

No I mean just because your vehicle is capable of 10,000 horsepower doesn't mean when using it every day you are using that power.

When someone says I have 740 hp and I use it everyday for 70,000 miles I call that BS.

OH so you mean your not using ALL 740H. P. ALL THE TIME ? O. k. I hear ya there...




But it's sure nhice to know that its there under right foot when you want itOo. ... ... . :-laf

 

[Turbo Thom]

740 in a duro driven every day on no2 is too. I mean BS.