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Cost to power gain ratio... 6.5L vs 4BT vs 6BT

Discussion in '1982-Present GM Diesel' started by PhoenixZorn, Oct 11, 2006.

  1. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    Very simply, which engine do you guys think is the most cost effective to build to "max" power and torque? Now that I own a 6.5L, I have my own opinion on the matter, that for less actual money, you can have the same power in a 6.5L that you can get out of an absolutely blown 4BT...

    Max power numbers in trucks are close to 300hp and 500ft-lbs for both the 6.5L and 4BT engines, possibly a tad more if you figured out a new mod for the 6.5L, but that seems to be the "safe" max...


    Max power numbers for the 6BT is obviously higher, but in my opinion should cost more in the long run, especially if everything you do to it is mechanical in nature... My former boss is currently running around 340hp and 700ft-lbs in his 97 Dodge Dually... and I met a Diesel Tuner Dyno guy last year at TDI Fest who's 02 Dodge Dually was puting down a tremendous 1200ft-lbs of torque (sorry, don't remember his hp.) The 97 was all mechanical mods, and the 02 is mechanical mods plus computer mods.

    The things I know...
    • a 300hp 6.5L custom built engine costs about $10,000 from Peninsular Diesel, and that to build the same motor in your truck it would cost about $4000-6000. A new "Stock" 6.5L engine runs about $5000 in case you needed to start from scratch, and comes with 195hp/???ft-lbs of torque for the 97+ model. That's a good start.
    • a new 4BT costs somewhere in the neighborhood of $4000... it starts out with 125hp/250ft-lbs of torque... enough to move our trucks, but it NEEDS mods to be effective. Incidentals include tranny adaptors, fabrication mods, fitment... Add in all the mechanical mods my ex-boss has on his truck, about $3000, and you are already at $7000 for just the motor and mods, not including the actual cost of installation.
    • a new 6BT is just well... unreasonably priced... around $10,000 if memory serves, and it puts out something like 230bhp/330ft-lbs stock... in the 12v version... add in the same $3000 for mods, and more for fabrication and fitment...
    So, being that you can get a reliable 300hp/500ft-lbs out of a 6.5L TD, why would you go to a 4BT or 6BT? The ony reason I can see switching to a 4BT is the improved mileage... promises of 30+MPG in a K5 almost made me put one in my own truck... The only reason I can see switching to a 6BT is the possibility of more power later down the line... and I know the used ones don't cost that much, but can you really keep your total cost under $4000-6000 and get 500ft-lbs of torque in a 5.9L? Likey, yes... and the promise of being able to go even further would tempt me, but do I really need 1000ft-lbs of rear wheel torque in a blazer? I think not.
     
    Last edited: Oct 11, 2006
  2. bear76

    bear76 1/2 ton status

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    Show me where to get a NEW 4bt for $4000.00 and I'll tell you how it is when I'm done. 6BT is the most effective IMO. But the wieght is the downside.
     
  3. bear76

    bear76 1/2 ton status

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    Also, why do you need 500lbs of torque other than having 500lbs of torque. 300-400lbs would be more than enough for most applications. If you need more umph start with gearing and doublers to get it, it's cheaper.
     
  4. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    Wheeling aside, puting more power to the pavement in general is a nifty concept... you can't do that with doublers, and I already have 4.11 gears so I don't plan on going any higher...

    What applications are you referring to? A STOCK 6.5L puts out 190hp/380ft-lbs of torque before 1997, and after 1997, they put out 195hp/430ft-lbs. While that's enough to haul your 14' popup camper or your 18' boat to the lake reliably, it probably won't get it done fast or with any sort of decent mileage. Having the extra 100+hp and 100+ft-lbs of torque under your foot not only gets the job done more quickly, but you actually gain MPG with higher hp in most diesel applications because the engine doesn't have to work as hard to produce the same power it was before the upgrades.

    Similarly, if I'm on the trail and I have the option to drive a 380ft-lb truck or a 500ft-lb truck, you can bet I'm picking the one with more just for the simple fact that I can put more power into the tires, no matter how you look at it. Remember these engines are making peak torque at about 1800RPM, and get 18-22MPG while doing it... at highway speeds that is...

    Don't get me wrong, I love the 4BT, and I'll get you a link to buy them used if you are interested... there's something about that 30+MPG in a Blazer that still gets me.
     
  5. bear76

    bear76 1/2 ton status

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    Used I can find, I thought you said new. As far as hauling goes my 305ci pick-up has pulled 5000lbs cars around town. It wasnt fast but it did the job. Diesels dont always make better MPG with more power. You still have to put more fuel in to get the power.
    I can understand the need for more power but don't look for MPG's at the same time. A 4bt can also put out close to those torque numbers as well. It's just a 6bt with two cylinders lopped off, but don't expect 30 mpg's. Bigger turbo and more fuel is all you need.
     
  6. PhoenixZorn

    PhoenixZorn 1/2 ton status

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    bear76, if we could, I'd like to move this discussion back to the garage, just because it's more viewable there, and because it's annoying as hell to reply to two different threads... I'll change the subject heading on that one to match this one...
     
  7. kennyw

    kennyw N9PHW Premium Member

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    I paid less than $500 plus extra parts on trade (approx $1400 total value) for a good used 6BT with 230K. By just simply turning up the pump I had more power available than anyone could get by adding a banks kit to the original 6.2L in my truck. However with the cost of changing the other parts I decided to sell my 6BT and buy a $300 factory 6.5L turbo setup and a $200 gear splitter OD box for my SM465. I'll have more than enough power for my needs for under $1000 by the time I'm done.
     
  8. Rob 85K5

    Rob 85K5 1/2 ton status GMOTM Winner

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    More info on this please??
     
  9. kennyw

    kennyw N9PHW Premium Member

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    Ebay find... older version of a Ranger OD unit that Advance Adapters now sells.
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I gotta disagree...and will point to the fuel mileage difference between a 6.5 TD and a NA 6.2 to back it up. To get the more power out of a diesel you need to add boost, and more fuel. More power still...more boost and more fuel. It'll use the same or more fuel cruising (because the fuel rate has been turned up.) It'll use a ton more fuel if you get on it...because it can. "ain't no such thing as a free lunch" applies.

    The best you can say is that with a turbo it is more volumetrically efficient.

    Rene
     

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