6.7 short comings that need to be dealt with

[JDinNY]

I've got an '08 with 89k miles. Deleted at 45k and no issues what-so-ever

 

[Bob V]

First, high turbo drive pressure will not blow a head gasket,combustion pressure is about 30 times the highest drive pressure, IF drive pressure can blow a gasket it would be an exhaust manifold or EGR cooler (or damage the cooler its self). Second, these trucks with the 6.7 ARE designed to also run without the emissions in some over seas markets. Third, there are lots of people with deleted truck and are very happy (like me) and get better MPG and MUCH cleaner engine oil. Forth, yes, you WILL see more head gasket issues with deleted trucks, but not because they are deleted. It's because deleting is the first thing a "hot rodder" will do with these trucks, then they will abuse them and that is where the problems start. Fifth, messing with the fuel and emission has ALWAYS been illegal, even with the 12 valves. Same laws are broken changing a cam plate, injectors, turbo, etc, on a second gen as removing the DPF/EGR on a 4th gen. To the original poster, if you go to www.cumminsforum.com you will se a lot more info on deleted trucks. I am not saying you NEED to delete, it's up to you, but get ALL the info first, then decide, and, if you don't like, you CAN always go back.

 

[AH64ID]

Drive pressure itself doesn't do anything, but it is an indicator of lack of flow thru the motor which increases cylinder pressure and that pops the HG.

With the increased bore and siamesed cylinders the 6.7 is harder on head gaskets than the 5.9 for the same airflow and power, the added timing of a tuner, even on low levels, increases the cylinder pressure... But also decreases EGTs, increases fuel economy, and driveability... To a point.

 

[Bob V]

Are you SURE that lower air flow through a motor = higher combustion pressure? If you think about it, it should lower peak pressure. Less FRESH air would be less oxygen and smaller "Bang". Its how EGR work, replace "fresh" air with inert gases lowers combustion pressure.

 

[AH64ID]

Yes. There is a direct link between drive pressure and blown head gaskets, the cam timing must allow for decreased exhaust flow but normal intake flow, which results in higher volumes in the cylinder and the resulting pressure.

 

[Bob V]

But you just said the high drive pressure "is an indicator of lack of flow THRU the motor", now its just lack of flow out the exhaust?

 

[AH64ID]

Well the air goes in easily, but not out. A lack of exhaust flow keeps the air from flowing freely thru the motor.

 

[cerberusiam]

The turbo is still boosting air into the cylinder and if it can't get out it stacks up the only place it can. The fueling curves, and turbo operation, are predicated on the EGR dumping oxygen depleted air back into the intake to displace the oxygen rich charge. When that is lost you have abundant oxygen to spike the cylinder pressures. The EGR system acts as buffer to keep the DP from spiking high when the turbo slams shut, the DP forces more depleted charge into the cylinder to control temps and pressure. With the EGR system blocked that safety valve is no longer there and there is no compensation control on the fuel\air mixture.

Getting rid of the stock turbo and using a single or compounds that by design reduce the DP takes a lot of the problems away. Then all one really has to worry about is over taxing the existing design with heat. The fact the engines are used in other regions without the emissions stuff is irrelevant, tuning for non-emissions is a enough different that the problem does not arise. The 6.7 will always have problems HG reliability when pushed to far, it is inherent in the design. They far more than the 5.9 require o-ringing and head bolts to control the movement of the head and block.

 

[Bob V]

Well the air goes in easily, but not out. A lack of exhaust flow keeps the air from flowing freely thru the motor.

I thought that is what I said? I know a LOT of people are CLAIMING drive pressure is blowing head gaskets. I do NOT buy it. I learned a long time ago just because its on the internet doesn't mean its true. How many blown EGR coolers are misdiagnosed as head gaskets?
I am not trying to start an argument, I just want proof, not internet rumors.

 

[AH64ID]

Getting rid of the stock turbo and using a single or compounds that by design reduce the DP takes a lot of the problems away.

HE451! Plug and play, keep the exhaust brake and a much better turbo.

I thought that is what I said? I know a LOT of people are CLAIMING drive pressure is blowing head gaskets. I do NOT buy it. I learned a long time ago just because its on the internet doesn't mean its true. How many blown EGR coolers are misdiagnosed as head gaskets?
I am not trying to start an argument, I just want proof, not internet rumors.

When the EGR is MIA it's prettying hard to misdiagnose.

I agree it's not DP, DP is just the indicator of the issue. Too much DP to boost is when they pop.

 

[CBlack]

This thread is full of BS.

I've been free of fuel economy/power reducing equipment for 70k miles or so. I've used Smarty and EFI Live, from 30hp to 120hp. Guess what? NO HG issues, period.

I am seeing 22mpg hwy and 18.5mpg city. You free yourself of the tiny VGT turbo and the head gasket issues pretty much go away. In fact, I haven't heard of many, if any, HG issues for a few years since the likes of Smarty, et al have learned how these engines work.

The 6.7 was designed to work without the EGR/DPF system. The EGR/DPF system was designed to work ON the 6.7 engine.

 

[BDW]

I'm living free and clear now myself with my 6.7. Had a few issues with emissions in the beginning before I installed them in the shop. I have a little over 150K on the truck and haven't even had to put brakes on yet. Just a little preventive maintenance when it comes time. I do not work my as hard as some but when it works it is usually pretty hard.