in-line 6 Cylinder Engines, 'straight-six'

Discussion in 'Propulsion' started by brian eiland, Jun 26, 2012.

  1. Milehog
    Joined: Aug 2006
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    Milehog Clever Quip

    The 6-71, being a two cycle engine, has twice as many, smaller, power pulses (think hits) as a 6 cylinder four cycle engine at the same RPM. Hence the smoother feel and screaming exhaust note.
    Edit; WVH was typing at the same time as I was, he just hit send sooner...
  2. whitepointer23

    whitepointer23 Previous Member

    the chrysler slant 6 was very popular here in boats , cars and dodge trucks, heavy on fuel but could pull a tree stump out of the ground. my father had 1 for 14 years and never put a spanner on it. i know someone else who tried to blow 1 up, he put a brick on the accellerator and it ran at full revs in neutral until it ran out of fuel, he said the only way to kill it was to drop the oil and run it. great old engines. this thread takes me back to when you could fix an engine with some spanners and a spare set of points, makes you wonder how much better things are now when you have to have a fancy computer just to tell whats wrong with your fancy computer.
  3. Frosty

    Frosty Previous Member

    It could pull out a tree stump because of the length of the stroke. The length of the stroke needed the engine laying at a slant so it would fit under the bonnet
  4. WestVanHan
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    WestVanHan Not a Senior Member

    IIRC they were oversquare..the stroke being just over 3" (80 mm or so)...about the same as the usual 2.0 litre ( 86mm x 86mm) 4 cylinder.
  5. sabahcat
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    sabahcat Senior Member

    vertical 265's are a powerhouse as well

  6. CDK
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    CDK retired engineer

    My post was about European cars, not Australian.
    I've owned several cars with straight 6 engines, the worst were two AMC Pacers, one to drive the other as spare part donor. That didn't do much good because design weaknesses are evenly distributed. When the exhaust manifold of one car cracked, the donor car manifold showed the same cracks in the same place.

    As a mechanical engineer, I favor short crankshafts in compact engines. The construction can be lighter, cheaper and produces less noise. In theory a straight 6 is a nice concept, but the torsion in long parts requires overly heavy constructions.
  7. CDK
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    CDK retired engineer

    I think Mercedes Benz has an impeccable design reputation, they put quality before costs. So they equipped their ML four wheel drives with 5 cyl diesels for Europe, V8 gasoline ones for the US markets.
    Audi/VW also uses 5 cylinder engines if 4 did not generate sufficient power, although the bulk is again 4 cylinders because they finally admitted that the common rail concept is better than their own "Pumpe-Düse" system.
  8. liki
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    liki Senior Member

    4 or 5 cylinders has nothing to do with injection method used, right? Used to own a Sprinter with MB 5cyl common rail engine.
  9. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The L6 configuration is dieing out for obvious engineering issues. Most everything an engine is used in, is being made smaller and lighter, so an L6 arrangement gets tossed right away, for it's length and massive rotating assembly, which has to be more robust, just to support itself. This is one reason the L6's of the world have good reputations. Their necessarily big, heavy cranks produce a fair bit more reciprocating mass, for their displacement. This can be great in slow turning, slow responding engines, but again this is directly against the general engineering trends across most industries. Lighter, smaller, faster responding, more efficient engines are what's being drawn up, so an engine with a meter long crank isn't reasonable any more. V configurations can half the length of an engine with the same displacement. Opposed configurations can do the same as well as dramatically lower their height. The boxer configuration has a lot going for it, but hasn't really caught on as much as you'd think it should.

    As to the "fondness" of the good old days, when you could do a tune up with a match book cover and butter knife, well, I suggest you take off those special glasses. You know the ones that let you see only what you want to see. You seem to forget that those same, easily tuned engines also needed a fresh set of plugs every 15 - 20 thousand miles, valve jobs every 50k and getting them to survive past 100k, without having to carry a case of oil in the trunk, was not reasonable. Current engines, with those damned computer controls, can run with the same set of plugs for 200k without question. In fact, you can buy a new car, never open the hood for 100k and it'll be fine. I've tuned late models with over 100k, that still have the original oil filter, air filter, spark plugs, plug wires, the works. Try that on your 1963 slant 225 Plymouth Valiant. It would have spit out or burned up it's oil long before, the valves would be choked with carbon, the plugs changed a half dozen times, those solid lifters adjusted a few times and the leaks, sweet God the leaks, that you can follow home if you ever lost track of it. Yea, the good old days, when 100k was the usual life of an engine, before you strongly considered rebuilding it. Now 300k shows the cylinders are worn by .008" with modern engines and those confounded computer controls. By the way, those pesky computers have the same family of engines producing twice the HP, 3 times the longevity and twice the fuel mileage too. Yea, the good old days my butt.
  10. powerabout
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    powerabout Senior Member

    plenty of ozzie inline 6's ( including the slant 6) would do 150,000miles plus only changing the oil
    taxi's well into the 200,000 miles
    Must be your low quality fuel in the US?
  11. powerabout
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    powerabout Senior Member

    Inline 6 is best for a diesel and that why they almost all are
  12. whitepointer23

    whitepointer23 Previous Member

    i realise there is an advantage with modern engines but when your 100 miles from the nearest town and the efi pump craps out or the ecu you are not going anywhere. at least you can clean out a carby or fix the points and get to town. i agree with what you say par but you are over exaggerating a bit. we have much better oils now which would have helped the old engines. i have seen 250 falcon sixs reach 500,000 miles . my 2007 model gt falcon has quad cams , variable valve timing and all the other fancy stuff but it only puts out 50 hp more than a 1971 gt with a pushrod engine and carby.
  13. whitepointer23

    whitepointer23 Previous Member

    i wasn't having a go at you, just pointing out that the l6 is alive and well down here, definately the most popular engine for the last 50 years . the
    ford barra is the last 1 on the market now and its days are numbered, not because there is anything wrong with it but because ford australia are losing 300 million a year so they are changing to an imported 4 cylinder. our car industry is in deep sh#t with all the cheap imports they have to compete with.
  14. whitepointer23

    whitepointer23 Previous Member

    barra drawing and pic of e38 straight 6. par you would be in heaven playing with those triple webers.

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  15. powerabout
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    powerabout Senior Member

    Ford got a patent on the variable induction
    How many production cars have that??
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