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Cummins Vs. Cat Diesels

Discussion in '1982-Present GM Diesel' started by Diesel Dan, Sep 20, 2004.

  1. Diesel Dan

    Diesel Dan 1/2 ton status

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    This is a continuation of a thread in tow vehilces.

    Not trying to start brand wars. Just looking for some comparision info on engines I'm not familiar with.

    Blueblazer62 stated:
    "The base engine is better and stronger in many ways,"

    In what mechanical aspects are you refering to?
    Lots of people are familiar with the Cummins 6BT/ISB, but lets get some info on comparible Cat 6 cylinders.

    Heck, bring on the +/-'s for anyother I6 turbo diesel!
     
  2. joez

    joez 1/2 ton status

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    For a tow-rig only, i would rather have a cat. They are simply stouter motors. Yeah, the cummins is easier to bomb, but if this is only a tow rig, then i dont need to bomb it.

    I would LOVE to have a 3126B CAT in an 80's K or V 3500 crew cab dually. In highway form they are offered in power outputs that range from 190 hp and 520 ft/lbs, all the way to 300hp and 860 ft/lbs. An edge box and that can be bumped to 340hp and nearly 1000 ft/lbs.

    But, it would be much easier to swap in a 3208T V8 diesel from an 80's rig. Mechanical, still plenty of power, but heavy.
     
  3. blasterD

    blasterD 1/2 ton status

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    Is it possible to fit a 3126 CAT in an 80s Chevy? IIRC I thought they were too long to fit in the engine bay.
     
  4. BlueBlazer

    BlueBlazer 1/2 ton status

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    First off, a little background. I have personally overhauled two 5.9s. One rotary pump Ag engine and one Dodge engine that I used to own. I have overhauled at least 10 3126s or C7s and have done TONS of injector and turbo changes on them as well. The 5.9s were rebuilt about 2 years ago, so some of my memory is fuzzy on them, so bear with me.

    First, you should know if you do not already that both engines are designed to do different things. The Cummins in a Dodge is designed more for light load use for shorter bursts while the comparable Cat engines are made for more continuous heavy load use. This means that the Cummins turns faster, makes more hp, but has less peak torque. Another major difference is the fuel systems. The Cummins uses a p-pump which is WAY overkill for this size engine. I think Cummins used it because it was easy to adapt and was well proven on other engines. Also, it has a really good governor which is nice use in a light truck. Because it is so oversized, it is capable of tons of power. The newer VP44s and common rail system is also capable of flowing much fuel, though it sounds like those are closer to their safe limits when the get bombed, but I dont know for sure. The 3116 Cat uses a cam driven unit injector, which is very robust and lasts a long time, it is not as friendly to getting a lot of fuel out of. The injectors are expensive and basically you need a custom cam to get more fuel out of it. AFAIK, no one makes custom cams for these engines, thus, you are basically limited to power slightly above the factor marine rating (assuming you use marine parts like pistons, injectors, and cam). This is still a lot of power, like 500 hp and over 1000 ft lbs, but these numbers are obviously easily attainable with a Cummins. However, this marine rating is using factory parts, so being a factory rating, its been tried and tested and should last much longer at this power level. The newer Cats, the 3126 and C7, both use the HEUI fuel system like just like the Powerstroke. This system is capable of a lot more fuel with much better control of injection since it is fully electronic. These engines from the factory are capable of an easy 400 hp and 1000 ft lbs, but I would assume they could be pushed easily past that.

    The core engines are very similar at first glance. The cranks and rods are very similar. IMO, Cat bearings are superior, but the difference is probably negligible. The pistons, block, and heads are what really seperate the two I think. Cat uses pistons with either a steel crown and aluminum skirt or fully steel, where as far as I know, Cummins still uses all aluminum pistons. The block and heads are noticeably beefier on Cats, thus the extra weight. Basically, the Cat is made to last much longer at higher loads, but is not as much of a "hot rod". I am going with a Cat mostly for the cool factor and its where I work, so I have tons of knowledge to draw off of with these engines. Both engines are great, and I would have no problem installing either in a truck. /forums/images/graemlins/thumb.gif
     
  5. Muley

    Muley 1/2 ton status

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    You bring up some good data. Let me throw one question out here.

    I have always heard that the Cummins is a continuous duty engine. Meaning you can run it at the redline, all day long, and not affect the longevity of the motor.

    I gathered from what you said, is that a CAT motor is even better at doing that. Did I read that right?

    Granted both engines have different redlines and such, but they are probably build with the different RPM ranges in mind.
     
  6. joez

    joez 1/2 ton status

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    I dont think it is possible, but i can dream. /forums/images/graemlins/tongue.gif
     
  7. BlueBlazer

    BlueBlazer 1/2 ton status

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    It depends how much power they have and what parts they have been built with. You guys have to understand that there are tons of ratings for both the 5.9 and medium duty Cats. Everything from industrial, marine, automotive, machine, and genset applications. Generally, the lower the power, the higher the duty cycle. What I was getting at is that although the Cummins can make more power, it can not run at that power for more than short bursts, while a Cat can run at a lower power for much longer generally. It really comes down to what you want to use it for. Do you want a hot rod or a tractor? If you want a hot rod, you get a 5.9, if you want a road tractor, you get a Cat IMO.
     
  8. jerry303

    jerry303 Registered Member

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    Very good argument, the question is how the hell do I get a Cat in a 3/4t-1t vehicle at a reasonable price? What is available with this engine is what I'm asking.
     
  9. eightyone

    eightyone 1/2 ton status

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    anyone knwo how much these cat motors are goin for? and what it requires to get one into a 4 wheel drive 84 3500? and what type of tranny you would need?
     
  10. BlueBlazer

    BlueBlazer 1/2 ton status

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    You are going to spend a good deal of money on the engine and a lot of time making mounts and doing all the little things to make it work. Not worth it for most, but it will be to me.
     
  11. BlueBlazer

    BlueBlazer 1/2 ton status

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    What engine you want to use might be pertinent information for me to answer your question.
     
  12. Diesel Dan

    Diesel Dan 1/2 ton status

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    BB62,
    What is the CID on these CAT motors?
    I did see the steel pistons on a N14 Cummins getting a major at a Ryder shop once. Kinda weird looking with 2 piece pistons, if your not familiar with them.

    Correct me if I'm wrong here, but with the heavier pistons the motor should have a lower RPM range and it will rev much slower due to the high reciprocating mass. Since the Cummins appears to be over built for the LD truck market the Cat would have too be WAY over built.

    Long pulls at 400hp/1000TQ would wear out most any LD driveline. Imagine the load that would require that kind of power for a sustained period of time /forums/images/graemlins/eek.gif.
     
  13. BlueBlazer

    BlueBlazer 1/2 ton status

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    3116 is 6.6 L, 3126/C7 is 7.2 L. The heavier pistons do not really change the rpm range since so many other advancements in rods and bearings hold everything together fine, and if you dump enough fuel to a diesel with a correctly sized turbo, acceleration generally isnt an issue.
     
  14. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    anyone knwo how much these cat motors are goin for? and what it requires to get one into a 4 wheel drive 84 3500? and what type of tranny you would need?

    [/ QUOTE ] Back when I was interested in one I called Cat and they quoted me 10-12K for a complete crate 3126.
    For the manual guys I guess a clark 6 speed would be a good route but I'm not sure because I am not a manual fan.

    If it was me I would run a 6 spd Allison automatic with a divorced t-case.
     
  15. ben427

    ben427 1/2 ton status

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    I was just measring up a 3126 the other day. got a line on one and may pick it up. Its should fit in the engine bay withou too muchd ifficulty really, its not much, if any, bigger than a cummins.
     
  16. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    [ QUOTE ]
    I was just measring up a 3126 the other day. got a line on one and may pick it up. Its should fit in the engine bay withou too muchd ifficulty really, its not much, if any, bigger than a cummins.

    [/ QUOTE ] Yeah, they are almost the same size.
     

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