Can you tell me the merits of a v8 diesel vs straight design????

[BlueSky94]

Over the years, I've owned straight 6 and v8 diesels. Can anyone tell me why GM and Ford don't follow cummins/cat lead and make a straight 6 diesel?

I dont' understand the merits of a v8 diesel and they are clearly not a reliable.

I have an '03 cummins, a '98 6.5 suburban and have driven both the 6.6 duramax and the powerstrokes....Why in the world do GM and Form even make a v8 design.

[BobND]

My GUESS would be that the V-8's are shorter to fit a gas engine bay better, and not as high, allowing a lower hood line.

[JoeyD]

Cummins is coming out with new V8's in the near future so I can't say which design is better in the long run. GM and IH are not the only ones to make a V diesel motor.

[Bobbie Martin]

Originally posted by BlueSky94:
Can anyone tell me why GM and Ford don't follow cummins/cat lead and make a straight 6 diesel?
I dont' understand the merits of a v8 diesel and they are clearly not a reliable.

..Why in the world do GM and Form even make a v8 design.

I'm sure its news to Cat & Cummins that their V8 diesels are unreliable. There is no inherent reliability in an inline engine verses a V or any other configuration for that matter. Well, maybe an "H". BRM never seemed to get it to work!

[BUZZ]

Inline block castings are with out question stronger than V blocks. Past that, I don't know.
Buzz

[gmctd]

Shorter stroke V8's tend to shove the pistons thru the cylinder walls in the direction of crankshaft rotation, resulting in greater out-of-round cylinder wear.

Really big long-stroke V8's with deep crankcases, do not create as much side thrust on the pistons.

The I-block, generally of longer stroke, and long rods, with the crank further from the cylinders, does not create as much side-thrust on the pistons, resulting in much less cylinder wear.

For identical displacement, the V8 is smaller than equiv I-block 6, so they got popular.

[joe hatfield]

QUOTE]I'm sure its news to Cat & Cummins that their V8 diesels are unreliable. There is no inherent reliability in an inline engine verses a V or any other configuration for that matter. Well, maybe an "H". BRM never seemed to get it to work! [/QB][/QUOTE]

There is a reason neither Cat, Cummins or Detroit make V-series motors for the commerical truck market. Cat and Cummins (not even sure that Cummins makes one anymore) V-series motors today are for industrial/heavy equipment use where they are in a very controlled, constant rpm/power delivery situation or they have no size restraints for the raditors.
Inline motors tend to cool better due to the fact they expose more block/cylinder surface to ambiant air and tend to wick away heat more so than their v-series counterparts . They do not have an intake manifold and turbo covering half the motor, keeping hot air from escaping to the atomsphere.
Are they more reliable? who knows.
As to Cummins building a v-8, I'm sure they will to keep up with the hot rod truck market. A I-Line motor will never do that as good as well as a v-line motor.
I can only hope it works better than the 903 we had in a Washington 78 log yarder. Lots of power, but man I got tired of rebuilding that motor!!

[MTTwister]

Bobbie: Well, maybe an "H". BRM never seemed to get it to work!

I remember that one - I might even have a pic of it at Watkin's Glen - way back!

AND on-issue - isn't the in-line 6 inherently balanced?

[Bobbie Martin]

WARNING COMPLETELY OFF TOPIC!
Bobbie:
I remember that one - I might even have a pic of it at Watkin's Glen - way back!
[/QUOTE]
Wow from the glory days of F-1! I still think the early to mid 60's F1 cars without wings look like "real" race cars. And the opening scenes of "Grand Prix" at Monoco on a good home theater - it just doesn't get any better. About the H16, maybe it was the two crankshafts geared together that doomed it. What were they thinking? Twin cranks, 8 cams and there was a 4 valve version for a whopping 64 valves! Talk about complexity! How would you like to time that puppy?

[jdmetcalf57]

I remember a professor saying in engineering school (a long time ago) that an inline 6 is the most inherently balanced design engine.

My brother has owned a lot of farm equipment diesel engines over the years and he says that he has not seen any V-8s hold up as well as the inline 6's

[dieselhumvee]

inline six cylinders typically have 7 main bearings vs 5 for the typical V-8 design. More main bearing surface area = less main bearing wear. In the case of the 6.2/6.5, if we had a couple more mains, we would be much less likely to have these block cracks. Another benefit of the I-6 is that each rod has it's own journal, wehre the V-8 rods share a journal, so the rods/rod bearings can be bigger and beefier.

just my 2 cents, I wish Hummers had come with an I-6 diesel, but since 6.2's are so cheap to replace (compared to other diesels), I will just keep replacing them, they can be made to last 200K or more so I will replace an engine every 10 years... not a big deal to me.

[Robyn]

Ok Engine design 101
The V8 engine gives smoother power due to 8 power pulses instead of 6. The v engine is shorter and allows designers more flexibilty with the vehicle underhood design. The biggest problem with the V8 engines we have seen in our diesel pickups is that Ford and GM have always taken the quicky cheap route and never really finished the design work on any of there diesels. The 6.9 and 7.3 NA Ford (IHC) were designed by IH a long time ago and were pretty good power plants. The Power Stroke is the T 444E IH and is not too bad when IH does the complete package. The Ford electronics package left a load to be desired. The HEUI engines like the Stroke tend to be a bit more fussy as there is a lot more stuff to go south with the electronic injection.
The 6.2 and the 6.5 are fair except that they were made just a tad too light structurally. The block and the heads could be heavier and they would live a lot longer.
Cat now has had several good V8 engines The 3208 was a good medium duty engine except that it was a dirty engine emission wise and that was its downfall. The 3408 heavy truck engine was a terror and its demise was due to emissions and fuel consumption. The cummins VT 903 was just a bad plan all the way around. When they ran they were a powerhouse but they were a maintenance hog.
The Dodge Cummins is a great little light and medium duty engine. As with all new stuff the more electronics they bolt on the more problems that arise.

[toyboxrv]

Despite what a lot of people want to believe, an inline 6 is not more inherently balanced than a V8. The V8 has a piston and rod going down with another elsewhere going up while a 6 does not. There is no cooling advantage to an inline. The 6.2/6.5 has an open intake, one that doesn't seal the intake valley and that doesn't help with cooling much. The longer inline 6 has coolant going by more cylinders before it gets to the back and returns in the head. A better design on the cooling system is more important the configuration of cylinders. I talked to a friend who balances crank at an engine shop about balance and he said all engines except boxers must have counterweights to offset the piston/rod assembly and that an inline 6 has no advantage over an V8. The side thrust on either engine is the same, no advantage there either. Larger, fewer cylinders will produce more torque, but rev slower and make less hp than more and smaller cylinders. The Cummins has a very long stroke to bore and gets its torque advantage from that more than from being an inline 6. All of the currently available diesels in the big 3 are excellent choices and I wouldn't mind having any of them, but I wouldn't make my choice based on inline vs V8.