What makes an inline 6 engine more reliable than a V6 or V8 configuration? 3

[eouedu]

I don't want to start an engine debate but I know enough that generally straight 6 engines have a reputation for being more reliable than a V6 or V8 configuration. Just to simplify this discussion I want to stick with a discussion of older pre efi passenger vehicle and pickups engines because that is what I'm interested in. There aren't that many inline 6 engines out there but most of them have a very good reputation for being reliable.

-Cummins diesel all years but specifically the 89-98 "12 valves" are known to be very reliable
-Ford 300 straight 6 there are a lot of people including myself that would argue this is the most reliable gas motor ever produced
-Dodge 225 "slant 6"
-Jeep 4.0/4.2
-BMW inline 6
-Toyota supra inline 6
-HJ60 landcruiser diesel

Runners up:
-Toyota fj40 gas straight 6
-Mercedes 300D (inline 5 so doesn't get full credit)
-Chevy 250/292

These engines are often referred to as "bulletproof" or at the least are pretty well known for being very reliable. Especially when compared to their v6 or v8 counterparts.

Possible ideas that would contribute to the making them last longer than most V6 and V8s:

-less powerful so they aren't used as hard
-easier to access and work on therefore they are maintained better.
-less moving parts
-Power peaks at lower RPMs so it takes less to do more
-less prone to hot spots so less chance of detonation
-being upright gives more lubrication around the cylinder walls because gravity isn't working against the high side of the cylinder wall
-being upright applies the same theory for cooling and every other part where gravity could be fighting a v engine
-more bearings in the crankshaft (ford 300 has 7 main bearings)
-better balanced
-more surface area exposed to air and more open engine bay for it sheds heat better
-less nooks and cranies for old oil and engine particles to hide when the oil is being changed
-less parts of the engine hidden that aren't as well lubricated and/or cooled
-I don't believe any of the above mentioned engines have timing belts, it's either a chain or gears

If anybody has anything to correct or add feel free.

 

[BrianGar]

Quick thoughts....

Inline 6 has nice balance...
v6 and v8s have timing belts/chains a mile long plus lots of extra spinning stuff to cater for said mile.
v6 and v8s have 2 head gaskets, 2 rocker gaskets, 2 exhaust mainifolds and 4 cams.

I own an E39 inline 6 for the past 7yrs....spent most of that time at or near redline - driven very hard, always. Engine has never been opened, not even once for anything in that time so that makes me biased right away!

Bar a v12, the inline 6 is perfection in my opinion.

Brian,

 

[Lou Scannon]

Add a turbo, and it just gets better... near ideal 240 degree phasing between exhaust pulses, if the designer troubles to split the manifold in half front to back, and spec a twin entry turbine housing.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[LionelHutz]

Why must V6 and V8 engines have mile long timing chains and 4 cams???

 

[BrianGar]

@ Lionel,

I was moreso talking about the European ones...I guess there are Us hemis and such with pushrods and 2 valves, but we dont really count those in Europe and they are considered prehistoric in terms of design...

Brian,

 

[LionelHutz]

Yes, God forbid an engine has pushrods. Don't worry about the fact that they actually do work fine for moving a valve.

 

[BrianPetersen]

"Work" yes, but it's harder to do independent valve timing for intake and exhaust, and it's harder to do 4 valves per cylinder. If you want good emissions, and good fuel economy, and good power, and fit the engine transversely, and not approach 90/10 weight distribution, DOHC is the way to go (and there was another thread some time ago discussing this).

But this is scarcely relevant to the inline-6 versus V-configuration argument, since there have been both successful and unsuccessful combinations of every practical cylinder and valvetrain configuration. My van has a Chrysler 3.6 Pentastar in it, which is DOHC 4-valve with independent VVT on intake and exhaust, complete with the chain drives getting to the top of the engine. It has been good for me, and if there is any rampant issue with cam drives on those engines, I'm not aware of it. That engine replaced several other V6 and V8 engines in Chrysler's lineup, which were various pushrod and SOHC designs. The Pentastar has more power, better emissions, and is more efficient than any of the engines it replaced.

Still ... irrelevant to the inline-vs-V discussion. The Pentastar fits transversely under the hood of that van. The old inline slant 6 would not!

 

[LionelHutz]

Talk of complicated V8 DOHC schemes making the V8 less reliable doesn't have any relevance when comparing V8's against those old I6 engines.

 

[dgallup]

Good thing I don't want transverse engines. Please don't tell my C6 Corvette it doesn't have good emissions, fuel economy and power. Just try to package a DOHC under that hood.

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[BrianPetersen]

Nice car ... and it has a highly developed engine, pushrods and all. I sure wouldn't suggest replacing that engine with an inline six, either

 

[enginesrus]

Agree with Lionel, no savings at all with overly complicated valve actuation systems, when very expensive failures occur at very low mileage. And dare not have the correct paper work to prove oil changes, then you can be stuck with the 60K replacement cost of an engine, depending on the manufacture of course. Just my opinion.

 

[PackardV8]

I own an E39 inline 6 for the past 7yrs....spent most of that time at or near redline - driven very hard, always. Engine has never been opened, not even once for anything in that time so that makes me biased right away! Bar a v12, the inline 6 is perfection in my opinion.

No one example proves the rule. I have a neighbor who spits on the ground and curses when BMW is mentioned. He thought he was buying prestige and instead his E39-engined Bimmer bought endless trips to the dealer service department for major and minor fixes. Over the two years he owned it, it was in the shop more than he drove it and finally got out from under via the lemon law, but only after ugly hassles involving lawyers. It was his worst car in forty years of ownership.

Another poster here hates his IH V8 diesel and claims they're junk. A friend in Alabama who owns a fleet of rollback car haulers laments that he can no longer buy trucks with that engine. He says with regular maintenance, they ran forever; his most reliable engines in forty years in of medium duty trucking.

jack vines

 

[waross]

He says with regular maintenance, they ran forever; his most reliable engines in forty years in of medium duty trucking.

That would be the 7.3 that you cite as an example in a discussion of the 6.4
Different engines, different stories.
IH has made more than one V8. Some are better than others.
Mine has a bad rep.
The recommended oil change interval for the Maxxforce 7 (6.4L) is 15,000 miles. The IH service manager told me that one customer is changing oil in his Maxxforce 7s every 3,000 to 5,000 miles.
It's a good thing that there are lots of dog lovers out there cause this engine is a dog.
At the moment it is still running well and has less than 50,000 miles.
Anyone who thinks that it is getting a bum rap is welcome to buy it.



Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[SwinnyGG]

instead his E39-engined Bimmer bought endless trips to the dealer service department for major and minor fixes.

E39 is a chassis code, not an engine code- E39 is the 95-'03 5 series which came with many different engines.

The BMW I6 is known to be relatively reliable, with a few exceptions (water pumps with plastic impellers, noisy variable valve timing gear). The V8 in the 540 is bombproof, the V8 in the M5 less so... the I4 was a dog and did not requite itself well.

So there's a myriad of possibilities for someone to have a bad experience with an E39.