Dually power upgrade project

[razur65]

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.

 

[WarWagon]

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.

 

[GM Guy]

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.

 

[red]

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.

 

[WarWagon]

@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.

 

[GM Guy]

@razur65 hopefully we didnt scare you away.

Have you had the truck long? IMO I would get it healthy and see what she can do. Keep in mind torque does alot, you dont really need alot of power.

here is what mine can do on stock power and cooling. That said, mine are 5 speeds, so more power to the ground and less heat in the cooling stack.


Blue and Silver is sitting a 26,000 combination. handled it like a charm, ran in 5th if I wanted, but kept in 4th and slowed down some for the sake of the tires and bearings on the back trailer. flat western KS, some hills pulling out of creek bottom areas, but nothing long or bad.



Red and White 93 is sitting at 21,xxx combo weight. This one was the hardest I ever pulled a 6.5L, Christmas Eve 2015, Vail Pass, I70 East bound in the Rocky Mountains. a long 5 percent grade that transitions to 7 percent at the last.

(It is the pull that a 2011 6.7L Ford 1 ton Dually cant get a 18,000 lb trailer (plus pickup, so total closer to 27K combo) over 48 mph with the throttle floorboarded from a dead stop at Dillon to the summit. http://news.pickuptrucks.com/2010/11/chevy-vs-ford-in-heavy-duty-rumble-in-the-rockies.html )

Every hill prior to this I had always had plenty of power in 3rd, but not this. once we hit the 7 percent I had it pinned and it was still falling, finally had to give up and drop to 2nd and chug on up.

For bone stock, IMO they both do quite well. both are 5spds with 4.10s and are identical powertrain wise except for the year.

SO if that is what stock can do, imagine what just 20-40 horse more would do.

 

[razur65]

No sir, not scared away, just been really busy lately. Nice truck you have there and that's gotta make you proud pulling those loads.
As far as my horsepower goals, I picked a number based on what I read some of the Cummins engines used in conversions are capable of putting out with modifications. Wasn't really an absolute number, just making a comparison factor for the math equations. You're right I haven't really payed attention to torque as I should be with a diesel engine. Re-evaluating some of my ideas anyways, gotta get the big dog in the shop and start with checking the compression and see how much attention this motor needs first off.

 

[razur65]

@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.

Wait a minute, 20 year old truck is antique? Isn't that like saying a guy who is 50 is old?

 

[razur65]

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.

Thanks for input War Wagon, I am really thinking option 1 is going to be the main route, gotta get the beast in the barn and start checking over with compression test to see if I have any major problems developing. If that all passes good, which I believe it will because engine hardly burns any oil, doesn't constantly belch out smoke, and still runs strong when I need it to. Unfortunately I have had other projects blocking the doorway to get this one in!

 

[razur65]

Thanks for the input everyone, as I have indicated in some of the replies I am working towards option one of working up my existing engine a little more healthy.
I am also considering an option five for the long distance cross country trips planned for the future, getting an actual motorhome for those trips and not using the truck trailer combo for cross country travel.

 

[GM Guy]

well, if you keep the 6.5L pickup and find yourself in need of assistance out in western KS or eastern CO, look me up.