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Dually power upgrade project

Discussion in 'Project Central' started by razur65, Jan 2, 2018.

  1. razur65

    razur65 New Member

    Dec 5, 2017
    Central NY
    Happy new year y'all, thinking of more power for my GM 3500 summer weekend tow rig. So the following is my thought process, wanted to run my options by those that have been there done that for your pro / con feedback.

    Objective: looking for 275 to 350 horses, good fuel economy for road trips, longevity, durability, and ease of service if need be while on a road trip ie dealer or garage mechanic.

    So option 1, shovel money into existing 6.5, meaning probably complete fuel system high performance overhaul including pump and injectors, possibly cylinder heads and definitely better turbo. So with all that add new radiator, and a transmission performance rebuild. It's just money after all...

    Option 2: Dmax conversion, seen a few parts / rebuildable donor vehicles on Craig list cheaper than 5k could make this very appealing. Even two wheel drive DRW candidates that make upgrading rear axle to disc brakes and something other than 4.10 gears. Understanding would have to get entire cab, dash, electronics, etc to make project work, but already done so with my truck anyway. Used a Suburban to upgrade my interior from basic Cheyenne to full power locks and windows. Gutted interior including entire dash to upgrade.
    Just don't want a body lift, to allow piping to clear. I like the low pro 2wd look.

    Option 3: Cummins implant, again a few reasonably priced donor vehicles found on CL make this idea tempting. Horsepower modifications easily made, rumor has it these motors are extremely durable plus MPG figures discussed on forums even with modest horsepower modifications am plus that unmistakable Cummins sound out of a tailpipe. From underneath my fat ass Chevrolet tailgate would be the coolest
    Two choices of Cummins also sweeten the deal, earlier 12 valve so simple to run and modify or later 24 valve from complete donor truck of course to take advantage electronic diagnostic / tuning possibilities.

    These are the thoughts that plague me when I think about my truck project and which direction I should go. Wanted to get some feedback from guys that have had similar projects.
    Thanks all for reading.
  2. WarWagon

    WarWagon Well it hits on 7 of 8...

    Nov 15, 2009
    Option 1 is the cheapest and easiest. I as well as others have detailed that on here. Yeah drop in a Cumapart and learn how expensive parts are for it. At least you could keep it simple mechanical injection. Duramax would be an electronics nightmare however some on here @THEFERMANATOR can comment better.

    Option #4 is buy a pickup that already has the Cummins or Duramax engine in it. Even a Medium Duty truck is worth looking at as they are cheaper used than the everyone wants a diesel pickup craze. With the weight of your 30' 5th wheel I wonder how close to or over the towing rating of the pickup you are? DRW may make a difference. Regardless same money and a lot less effort has 4 wheel disk brakes, higher ratings, better cooling systems than the GM nightmare we got, better transmissions in the GM, MT in the Dodge is ok as their auto's suck and need a performance build from the word go... Pre 2007.5 emissions of course. Off the top of my head a 454 engine on this body style (SRW) can tow 11,000 LBS max. 6.5's are rated for less - why doesn't really matter as I explain below. My 2003 SRW Dodge can do 20,000 Combined subtracting the weight of the truck allowing ~13,000 Lbs for a trailer. Newer pickups handle even more crossing the CDL line.

    Patch, my 1993, doesn't have the rating to tow the 13,000 GVWR 27' 5th wheel I have. It's all the Dodge wants, but, within spec for it. So Option #1 may not work because of this...

    FWIW Don't overload your truck as far as the official ratings go. Never mind what it's capabilities are (improved engine, brakes, etc.) because the liability and your insurance company walking away from a negligence (overload situation) isn't worth it. Commercial insurance is different and more expensive, but, still not worth it.
    MrMarty51 and Will L. like this.
  3. GM Guy

    GM Guy Manual Trans. 2WD Enthusiast

    May 6, 2008
    NW Kansas and SC Idaho
    I guess we need to know the terrain you travel (flat land or nasty grades) and how big and heavy the trailer is.

    IMO unless the camper is a monster and you want to pull Donner Pass every weekend, I would stick with the 6.5L

    As far as weights, as long as you are within the GVWR and GAWR of the truck and trailer and not overloading the tires, you are legal. Hence the reason you see axle and total GVWR on the door sticker, and not a "tow rating"

    Tow ratings factor in acceleration. Identical C or K 3500 duallys can have a factory GCWR of 19,000 with a 454, or 14,500 with a 6.5L Obviously the truck is capable of the 19K, but the 6.5L wont accelerate strong enough (in stock form) to be rated over 14,500, so that is where it ends up.
    MrMarty51 likes this.
  4. red

    red stubborn Texan displaced to Utah

    May 17, 2008
    Eagle Mountain, Utah
    275-350hp reliably from a 6.5 towing, maybe with a P400. But unless your regularly towing in the mountains you don't need that much power anyways. I just finished a trip loaded at about 18k GCWR with a stock 6.2 diesel and was maintaining 65mph through most of the trip other than the mountains along I15 in southern Utah. Workin hard yes but no mechanical problems with just 135hp ish. Build up a 6.5 with better turbo and a few mods done by many here and it will work fine at 200-250hp range. FYI I'm not recommending a naturally aspirated 6.2 tow that much weight on the regular, it needs at least a turbo haha.

    If you're wanting to rely on shops to repair the truck along road trips then a older mechanical injected diesel is not the best option. Newer mechanics have been trained to deal with computers for diagnoses. Last shop I worked in about half the mechanics were this way. Let alone an IDI engine.
    Will L. likes this.
  5. WarWagon

    WarWagon Well it hits on 7 of 8...

    Nov 15, 2009
    @red One doesn't buy an antique and expect shops to work on it along the way. Conversions are extra complicated with parts that have to be made like drive shafts. Not likely to fail, but, I agree the shop or garage mechanic idea of the OP's is "out of line" for a custom or antique rig. Frankly the shops have a hard enough time with "Even in the future nothing works" late model vehicles.

    Although mechanical is "stupid simple" my latest DB2 replacement is delayed. Hell if I tried to order an Anvil UPS would find a way to destroy it. Short of that lost in shipping...

    You got to look hard for good shops. Harder for shops that deal with 20+ year old vehicles.
    MrMarty51, Jaryd and red like this.

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