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Jakebrakes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by fr8train, Aug 21, 2002.

  1. fr8train

    fr8train 1/2 ton status

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    Is it worth having a jakebrake on a trail vehicle? I know it would help slowing down, if you dont have the rear disk kit, but thats on the road.
     
  2. Shaggy

    Shaggy 3/4 ton status

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    <font color="green"> I've never even seen one offered for a gasser engine, just diesels. If and you have an auto it would be nice to have so you could use engine braking on descents. </font color>
     
  3. 70~K5

    70~K5 1/2 ton status

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    I use my jakes all the time on or off the road. Wait a minute, that's in my Pete. I've never seen jake in anything small enough to put in a blazer.
     
  4. jimmy88

    jimmy88 1/2 ton status

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    The true Jacobs Engine Brake is for turbocharged diesels and works by opening the exhaust valve near top dead center on the compression stroke. Its an old link but may still work;
    jakebrake . Does anybody know a site that explains how the exhaust brakes for diesel pickups works? Looks like they just choke off the exhaust pipe and can't be near as effective as a jake brake. The two bozo's on shade tree put one on a Dodge (i think) but I can't remember if they really explained how it worked. Anyway, unless an exhaust brake winds up being cheaper (after factoring in initial cost and engine wear and tear) than replacing brake pads, why bother? Is there some other benefit to them besides saving the brakes?
     
  5. fr8train

    fr8train 1/2 ton status

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    Sorry guys I guess I am forgetting to add that it would be for a 95+ 7.4L desiel in a trail vehicle.

    Jimmy88- good for on road use when you have to stop/slow a really heavy load and not cause a severe lock up/brake fade or wheel slide(inclement weather). As far as I understand the original Jacobs brake was rejected by the Jacobs top brass and so the original designer went to off brand companies for manufacter.
     
  6. wrathORC

    wrathORC 1/2 ton status

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    Somewhere I read about a guy or company that made a 700R4's torque converter lock up in first gear with a flip of a switch. I think this would be far better (simpler) than a jake brake and definitely more pleasant to the ears.
     
  7. 70~K5

    70~K5 1/2 ton status

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    They had those exhaust brakes under names like Blue Ox etc. Drove a couple of trucks that had them. Maybe they helped a little, but nothing like a Jake would.
     
  8. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    he he, more cost efectie way... and more fun.. remove th400(or equiv)
    and install NV5600.. he he. then ya got a lot better way of stopping...
    grant
     
  9. laketex

    laketex 3/4 ton status

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  10. jimmy88

    jimmy88 1/2 ton status

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    Good links. I could understand the Jake brakes on 50,000 pound trucks to assist their regular brakes but didn't know that a diesel pickup has no compression braking without an exhaust brake. That sucks, they should be stock from the factory. I checked out this link exhaust brake and learned that diesels have no intake butterflies like gas motors. So the exhaust brakes do the same as closing the butterflies on a gas motor. Makes more sense now, still sounds like they should come stock though.
     
  11. BlueBlazer

    BlueBlazer 1/2 ton status

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    Actually diesel powered trucks naturally have a lot of compression braking, since they are always taking in the maximum amount of air, and that air is being compressed by the pistons and a very high ratio, you get great compression braking even without an exhaust brake.
     
  12. jimmy88

    jimmy88 1/2 ton status

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    See the jake brake link; it says the energy used to compress the air is returned on the piston's down stroke. That makes sense, so the net energy loss would be from mechanical friction (not much energy absorbed) and the friction of moving the air through the engine and out the exhaust (prob not too much energy absorbed here either). Maybe someone who has a diesel can clear this up; when you take your foot off the gas, is there any engine braking or does it just coast? How does it compare to gasoline engine braking?
     
  13. m j

    m j 1/2 ton status

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    what is a 7.4 diesel?
    the smallest engine I have seen a Jake type brake offered for is a 10 litre Cummins
    though I think the old 2 stroke Jimmys might have them but not sure about that.
    to run a jake you require direct injection
    all the jake does is create a hydraulic link between the injection lobe of the camshaft and the ?exhaust? valve
    as most little diesels dont have an injector lobe on the cam a Jake isnt available, just the potatoe in the exhaust style is available.
    Powerstroke guys are lucky as newer ones have a flapper in place and just need to add a controller for it as Ford just uses it to decrease warm up time or something
     
  14. 70~K5

    70~K5 1/2 ton status

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    MJ I know they had Jakes for the 8V71 (318) and the 6V92 and up. Not sure about any other Detroit diesels but probaly the 12V71 had one too.
     
  15. m j

    m j 1/2 ton status

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    just for non truckin folk 318 is not the displacement 8 x 71 = 568ci

    if it was available for one of the Jimmys it would be available for all

    man that would be a riot to have a hopped up Jimmy in a 4x4
     
  16. 70~K5

    70~K5 1/2 ton status

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    Yeah 318 was the horse power. But a 290 cummins would run around it on a hill.
     
  17. BlueBlazer

    BlueBlazer 1/2 ton status

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    Uh, I do own a diesel, and yes, when I take my foot of the pedal it slows down much faster than a gas powered truck, even 454 powered trucks Ive been in with high compression.
     
  18. jimmy88

    jimmy88 1/2 ton status

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    Ok now I'm confused! Why bother with the exhaust brake at all then? If your towing something that heavy that you need extra brakes, then the trailer should have brakes. For trails I got a stock 350 with a 700r4 with a towing converter. Going down steep trails in low range it holds back well, so well I find I even have to give it some gas most times. Now if a stock diesel holds back better than a gas engine then what would be the point to a exhaust brake for trail use? It should work so well you'd go backwards! Just busting ya, but I must be missing something here because I just don't get the point of an exhaust brake if a stock deisel holds back better than a gas motor.
     
  19. laketex

    laketex 3/4 ton status

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    ever towed a 20K trailer up a mountain pass in colorado? I'd want every bit of braking i could get. Ever seen the runaway truck ramps? They're there for a reason.
     
  20. jimmy88

    jimmy88 1/2 ton status

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    Nah, only a 10k trailer to Ohio and Virginia a bunch of times, with a gasoline powered truck and no brake issues. And yes, Virginia had plenty of those ramps and I don't even want to think about what kind of ride that would be!! What light truck is rated for a 20k trailer? If the stock diesels hold back better than a gas motors, then for all but the really hard core tow rigs, isn't it just a pricy toy?
     

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