I’ve gotten a lot of emails asking what I think about the 6.7. These engines are stripped down so we can get to the basics of the engine very quickly. This gives an overview of the changes that have been made in the 6.7. The only way that we will know if the engine is worth a darn is when they get a few 100K miles on them and see what breaks. So far the only thing we have seen are turbo charger failures.
Turbo Charger: The turbo chargers in the 6.7 are a real serious problem. Ford Motor Company decided to put ceramic ball bearings in these turbos that are turning to dust, grenading the turbo and sending pieces down into the exhaust system which causes all sorts of troubles. However, this new engine goes reverse of what most engines do. The exhaust comes from the inside and goes directly to the turbo. This has a very positive effect of making the turbo spool quicker because there is less lag.
Injectors, valve covers and rocker arms: The injectors are serviceable without pulling the valve covers. Also, the valve covers are the intake manifolds. When you remove the valve cover, you are actually removing the intake manifold. With the valve cover off, we see that they solved rocker arm failure that was another common problem in the 6.4. The 6.7 has more rocker arms and push rods. By lightening up the valve train by taking all the extra pieces out, the push rods simply don’t wear out. Another new feature is this bar that sits across the top that squirts oil directly onto the rocker arms. This helps avoid rocker arm wear that we saw in the 6.4 around 100K miles.
Ease of serviceability: This is a 2012 with an aluminum oil pan not the plastic one that came on the 2011 and a spin on oil filter. The oil cooler is on the outside. It only takes a few minutes to change where the 6.4 was on top and difficult to get to. The designers of this engine kept a close eye on the serviceability of this engine.
18 head bolts: The 6.7 has 18 head bolts like the 7.3 and not the 6.0. There are 6 bolts around each cylinder, 18 total head bolts in each head as opposed to 10. We are talking about turbo charge diesel trucks with an aluminum head; you need all the clamping power you can get. Aluminum is much more prone to warping than the old cast iron cylinder heads. We have not seen head gasket failures in these engines so far, but tomorrow is another day.
Cylinder heads: The driver’s side cylinder head and the passenger side cylinder head are two different cylinder heads. The 6.0 and 6.4 had identical, interchangeable heads on the passenger and driver’s side. On the 6.7, the driver side cylinder head has an EGR block that goes into the block. The exhaust goes backward in this engine so it goes through a different path and the passenger side head does not have it. With the left and right cylinder head, you have a left and right head gasket. Also, the gasket themselves are only three layers. The earlier gaskets in 6.0 and 6.4 tended to have 5 layers. The head gasket is heavy and has some bulk to it.
There is an indentation on each of the cylinders between the exhaust valves. It is apparent that there has been a good bit of computer aided design and modeling to test these parts in a virtual environment and I am sure Ford did a tremendous amount of testing on this engine before they put it on the market. A big improvement in the cylinder heads is the addition of some real guides. With aluminum heads there is a steel guide to hold the valves with much tighter tolerances in the valve guide itself. There is virtually no back and forth play. That is a great improvement.
I am still a little freaked out about aluminum cylinder heads. There has had to be a huge jump in material technology.
Exhaust value: The exhaust valves are a good distance away from the injector and the glow plug is situated by the intake valves. This distance is important because it produces more cooling around these exhaust valves and helps exhaust cool therefore keeping heads from cracking. The beauty of aluminum is it dissipates heat much quicker and more evenly than steel. The heat is able to be extracted out of this combustion chamber area and keep the exhaust valves cool which is crucial to longevity.
Torque bolts, rocker arms and push rods: The torque bolts are the same ARP bolts in the 6.7; however, the rocker arms look like custom built stuff that you would buy for race cars. This is a heavy duty piece of equipment, not the little tip on there like a 6.4. The push rods are interesting. Instead of having a ball on the end like you would see on the 6.0 and 6.4, it has a cup on the end which means that the lifters have balls. The tips on them push against the push rod.
Lift points: The 6.7 has big lift points to avoid breaking the head casting on the aluminum head when lifting the engine. They pull from the iron block where it is much stronger.
Lifters and cam position sensor: The size of the lifter in the 6.7 is much bigger than the 6.0 and 6.4. There won’t be a failure point on the wheel rolling on the cam which was common and caused engine failure on the 6.0 and 6.4. The wheel is a great big ball bearing piece of equipment. The cam position sensor now looks like the 7.3.
Cavitation: After pulling the water pump, I want to point out cavitations, another problem with a 6.4, which ate the front cover. In the 6.4, it would eat a hole, cause water to mix with the oil and blow the motor up. In a 6.7 they fixed this by putting this out in the free air so if it does eat through, it would drip out onto the ground and not into your oil and kill the motor.
Oil pan and inspection pan: To get the front cover off, we have to drop the oil pan because there is a part that goes in here where the oil draws. The 6.7 has a small inspection pan that is easy to get to on the bottom of the motor. You can check it fairly quick and see if you are dealing with a serious problem. But to take the whole pan out, the motor is going to have to come out of the truck. With the oil pan and the front cover off you can see what six bolt mains or cross bolt mains are. You have the four bolt mains but then you have these two bolts that come in from the outside. This is an extremely strong design.
Bearings: When we took the piston out, we notice the bearings didn’t have keys on them. It is almost as if the bearings are machine fit to the connecting rod. I have never seen anything like that. It scares me to see a bearing with no key for fear of it spinning inside of the connecting rod but Ford has managed to figure out a way. To illustrate, the 6.4 rod has the key where the bearing has a notch that keeps it from spinning inside the connecting rod.
Rods: The 6.7 rod is much smaller than the 6.4 rod. Navistar had a large connecting rod on the 6.4 because the short end of the connecting was rod snapping. The smaller lighter rod by Ford helps with acceleration and performance but they had to make some giant leaps in materials that is not readily apparent to the naked eye. The only way you can have a piece that is smaller and be able to not have a connecting rod failure at the small end, would mean that they have made some significant change to the materials.
This specific engine failure: Once we removed the pistons from the motor, it became obvious that the piston was the problem. There doesn’t appear to have had anything ingested into the motor. The piston ring was fine, everything looked beautiful except the piston connecting rod that has a little bit of a bend in it. This would cause a vibration and lack of compression which would make the engine run poorly. When we looked at the cylinder head, the port going into this cylinder was just as oily and greasy as the one next to it so it didn’t appear to have anything be ingested that way either. But, at the same time on the exhaust port going up to the turbo charger, this particular cylinder was damp so there was obviously something going wrong. I am guessing that the fuel injector may have failed. When they cranked the engine there was fuel on top of the piston that got hydro locked and they just kept cranking until either the starter broke or the connecting rod bent.
So what did we learn from taking this apart? Ford learned from all the mistakes made with the 6.0 and 6.4, unfortunately the 6.0 and 6.4 owners had to suffer through it all. Better lifters, water pump, head gaskets, and all these improvements add up to a really good engine. Unfortunately it took the failures to learn how to improve. ~Bill Hewitt
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