What makes an inline six more reliable than a V8?

1. Way less moving parts. Less pistons, less rocker arms, less injectors, ect..... The more moving parts the more there is a chance to have something break.

2. In line 6 engines are smoother running than a V engine as the pistons are not fighting on another on a power stroke.

Not that it affects the reliability at all but look under the hood of a Dodge with a Cummins you can actually see the engine and even work on it for that matter. Look under the hood of a Ford or Chebby, other than changing oil what can you easily work on with those two diesel equipped pickups? Inline engines develop their torque at a much lower RPM. Less RPM's equals less wear and tear on the engine.

While Detroit Diesel had a long good run with V engine configuarations, the Cummins 903 is a POS, the Cummins 555 is a POS, the Cat 3208 is prone to crack the block around the main caps, especilaly if turbo charged. Cat 3408 is prone to block cracking and even crank cracking. All the engines listed above are very expensive to work on when repairs are needed.

Over the road trucks in the 70's thought V engines were the way to go, so did the agriculture industry and look at the change in the early to mid 80's and today, 99% of that equipment is all inline 6 engines.

V engines are used in big equipment applications such as trains, ships ect.... work well when spun at low RPM's but their use in an automotive industry at high RPM's is not good.

Just my two cents on the subject since I work in this industry.

Jeff

 

Wrong on that Inline 6s are "smoother". They have perfect primary and secondary balance, but the actually power delivery is not smoother. Part of the reason why people like I6 "smoothness" over say a 4 cylinder, is the fact that I6s HAVE over lapping power strokes, "fighting each other" as you say.

V8s have two more cylinders, and therefore have more over lapping power strokes, and have smoother power delivery. It may wont be as balanced as a straight 6, ie. the engine might shake a bit, or have some weird harmonics, but it will still be smoother. A V8, V10, V12 and V16 will all be smoother then a straight 6 (V12s and V16s can both achieve perfect primary and secondary balance like a straight 6 as well)

Have you taken a look at a 6.9/7.3 IDI V8 diesel? Those are about as simple as they get, and you can easily do a lot of work on them. Its all about the injection system and emissions, the more complicated the injection system and emissions standards, the more wires, hoses, actuators, etc.. going all over the place. Cummins used a relatively archaic injection system (compared to Ford and Chevy) upto 2002.5 or so before they finally went common rail. Take a peak under the hood of a 6.7 Cummins equipped Dodge, just as packed in with electronics and other components as the V8 diesels.

I6s making more torque is also BS. Its all about the bore/stroke relationship, even just the factory tune can make a big difference. Heres proof of this: The Navistar MaxxForce 7 (The commerical version of the 6.4 PSD) makes 620 ft-lbs @ 1400 RPM, while in comparison, the latest 5.9 Cummins generates 610 ft-lbs @ 1600 RPM.

Block cracking is more or less the fault of the engine manufacturer, not how the cylinders are aranged. Ask the Dodge folks about the "53" blocks

 

I do not doubt that the bore and stroke play a big part into the power on an engine, but the bore and stroke of the Navistar built engines used in truck applications were the same bore and stroke used in Ford applications. Navistar uses programing with low horsepower, high torque and low RPM. Ford used high torque, high horse power and high RPM's in their programing.

You are not comparing like to like. If you are going to throw a 5.9 into the picture you need to compare to the 6.0 (VT365). You have added displacement using the 6.4 so that would be more comparable to a 6.7 Cummins which last I saw had 650 FT LBS of torque.

On the Cummins website a VT903 twin turbo 14.8L V-8 has a max torque of 2086 (Nm). The current inline 6 (QSX 15) with 15L of displacement and a single turbo puts out max torque of 2542 (Nm). In the above example the V-8 has more horse power but lower torque.

 

The the Dodge Spec 6.7 cummins also has a displacement advantage, and generates that 650 ft-lbs @ 1600 RPM, vs. 1400 of the MaxxForce 7. Now the ISB 300 (6.7 commercial engine) generates 620 ft-lbs @ 1600 RPM as well. The Commerical 6.7 also has one more power level, the 325 HP which has 750 ft-lbs of torque, but at 1800 RPM!

In this case, it looks like Cummins is the one with the high RPM high HP engines, and its a straight 6!

I'm not trying to slam cummins, or navistar, but I'm just trying to point out that engine configuration has very very little to do with how much torque it makes, and at what RPM it makes it at.

 

I was just hoping for a 7.0l I6 sleeved engine with a Cat emblem on the side. It was more for the reputation and sound than anything else. They(The Big 3) have had their share of the problems, but in the little I know(nowhere close to most of you) the simplest of problems has to be with the Cummins. The Navistar 6.0L and newer have soured a lot of peoples' opinions about diesels in Fords. My favorite engine is the Cummins, but unfortunately I can't stand the TRASH built around it. Chebbys in my opinion are worthless as far as real work goes, and again this is just my .02 cents worth and not intended to start a debate about what is better.