Jump to content

Perspective on 6.6 Gasser

TrailBoss1

By TrailBoss1
in 6.6L Gas V8 (L8T)

 Share

Recommended Posts

TrailBoss1 Enthusiast

TrailBoss1

Posted
Posted

In the past, I drove primarily diesels; including a 2016 dually I traded for my current Trail Boss. I tow a CC fishing boat that weighs about 5,500 pounds loaded and certainly don’t need a diesel for that. But, towing with a 1500 after the dually, made me decide I just prefer the HD “feel”. In part, the extra weight increases stability. I owned one HD gasser many years ago (when the 6.0 was 300 hp/360 tq) and it felt adequate.

 

in looking at the new 6.6 gasser, I pulled up specs on the older 8.1 liter Vortec big block. That motor made 350hp / 450 tq (and could be paired with the Allison). So, the new 6.6 with 401 hp/464 tq makes significantly more horsepower and slightly more torque than the vaunted 8.1 big block.

 

i realize the new HD is heavier and larger than prior generations. Nonetheless, I think this gives me more confidence in the adequacy of the 6.6 for my needs. Is anyone towing a similar sized boat and, if so, your thoughts?

TrailBoss1 Enthusiast

TrailBoss1

Posted
  • Author
Posted

Thank you!! I recall the 6.0 wasn’t very good on gas either. But, I have a company vehicle during the week so I only drive this vehicle recreationally; about 12,000 miles per year.  I loved the torque of the diesel but the LML concerned me due to issues with the CP3 pump; and the LP5, while using a different pump, still comes with increased cost, maintenance costs and complexity. So I think the fuel mileage on the L8T is a reasonable trade off for my use.

Stand By Enthusiast

Stand By

Posted
Posted

I have a Chris Craft 251 express hard top. 350 straight inboard, rated almost 5000 lbs dry. 2 axle aluminum trailer, full 75 gallon tank, gear, 3 batteries. Only one trip this summer, over an hour drive each way on a winding, hilly road. Pulled like a dream. 2 5/16" ball on a forged, 3" drop insert. A rough measurement was that I still had about a 3/4" rake on a paved, level road. To be fare, my inboard sits almost center over the trailer axles. I would happily be making more trips if the boat engine didn't develope a hiccup on this last trip. Tow mirrors were great, too.

TrailBoss1 Enthusiast

TrailBoss1

Posted
  • Author
Posted

Thanks so much. That’s a very cool boat and weighs much more than my Tidewater 230CC (about 3,300 dry before gas, trailer, freshwater and fishing gear). Good luck getting things sorted out with the boat engine; Ive heard it said they are holes in the water we throw money into!! LOL!

  • Like 1
Rebel Rouser Enthusiast

Rebel Rouser

Posted
Posted

Well as the proud owner of one of those “vaunted 8.1”s with the Allison, I’m a little partial! ? But I test drove a new crew cab High Country. I was impressed with the size, the weight, the cab, the tech, and to an extent, the ride. I was not impressed, however, with the power band on the truck. From a dead stop, my big block will absolutely ROAST my 35” A/Ts and chirp out of 2nd gear. Granted, I have 4.10s, intake, headers, custom true dual exhaust and a canned tune, but I did expect more from the advertised numbers from the 6.6. I floored it coming out of the dealership expecting it to pin my eyes back like the 496 does.... not so much.
 

Higher in the RPM band, it really picked up and THEN it was impressive. So I looked up the torque curves for each engine and confirmed my suspicions. The torque curve on the 8.1 is incredibly flat comparatively. And the 8.1 starts off from idle with 400 ft lbs.  The 6.6 on the other hand, starts around 350 ft lbs from idle but climbs. However, the 8.1 reaches peak torque at 3200 RPM whereas the 6.6 is a little later at 4000 RPM. The big difference other than off the line is the horsepower. Over 4000, the 8.1 falls on its face thanks to a terrible intake design. The new 6.6 is a BEAST over 4000 RPM. I think when tuning companies come out with software for this new 6.6 motor, it will be unstoppable! 

52C2A3FE-FF8F-4AA1-B658-EA5B23D54289.jpeg

7EE24507-B4F9-464C-9D7B-0E1189FB6736.jpeg

Colossus Senior Enthusiast

Colossus

Posted
Posted

You've also got a TON of torque management on the newer stuff.  They don't want you to roast the tires, (or the rear diff in the process) they want you to have good traction on acceleration. 

Colossus Senior Enthusiast

Colossus

Posted
Posted

Yup, I bet once the tuners get going, there will be even more happy folks out there.  I am running a 3 stage tuner for my Duramax that are fairly conservative as I don't want to limp the thing (allisons are great trannies but if you push them too hard you'll toast them and limp mode them)  The tunes turn off the torque converter to some extent which makes a huge difference for me.  Not enough to roast the tires unless I power brake, but that would be stupid as the G80 rear diff isn't made to do that and I don't need to spend $2000+ for a new diff.  But getting on it is much more fun now.  I was able to pull on a 3.5L ecoboost F150 from a roll and he was not happy about it as he had intended to cut me off to make a left turn.  Having the top speed limiter adjusted to 120+ also meant I could accelerate strongly all the way thru 100MPH after he let off and so did I. 

TrailBoss1 Enthusiast

TrailBoss1

Posted
  • Author
Posted

Very cool you have the 8.1. I didn’t mean to imply “vaunted” as a negative. It was a compliment in every sense; that big block didn’t need a lot of technology to make power. Makes sense the displacement produces better low end torque. Hell, I thought my 85 Z28 with the LB9 was impressive making 215 HP from 5 liters. But, comparatively, the 6.6 makes almost 100% more power from a 33% increase in displacement (roughly). I’m looking forward to mine arriving; though it’s probably 10 weeks out.

Rebel Rouser Enthusiast

Rebel Rouser

Posted
Posted

No offense taken good Sir! I’m just glad GM is even going in that direction. You are correct, the stock numbers on the 8.1 are pathetic in terms of hp to cubic inches. Raylar fixes that problem, but my kids still have to go to college so I don’t have a 529 Roth for the big block yet ??

 

But, turning the TM off and running a premium tune after you open them up and let them breathe, and the 8.1 reminds you what unbridled instant torque felt like in the late ‘60s/early ‘70s. Puts a smile on my face every time I drive it. I hope the 6.6 does for you and that’s all that matters. 

nick112288 Enthusiast

nick112288

Posted
Posted

I'm just waiting for someone, somewhere to come up with SOMETHING for these engines.

 

The new Ford 7.3 already has a couple companies with tuners out, a couple intake manufacturers, at least 1 header company, Whipple and Procharger are getting ready to release systems.

 

Can't find anything for this 6.6l.......

Colossus Senior Enthusiast

Colossus

Posted
Posted

GM makes it very hard for the aftermarket companies on purpose. 

  • 2 weeks later...
Rmedic New Member

Rmedic

Posted
Posted

Just picked up a 2500 HD with the 6.6, to replace 1500 Sierra that just couldn’t cut it towing my 7500 lb boat, my question is, what is the recommendation for break in period before I hit the road with boat in tow, if any, thanks in advance.


Sent from my iPad using Tapatalk

Limelight Enthusiast

Limelight

Posted
Posted
2 hours ago, Rmedic said:

Just picked up a 2500 HD with the 6.6, to replace 1500 Sierra that just couldn’t cut it towing my 7500 lb boat, my question is, what is the recommendation for break in period before I hit the road with boat in tow, if any, thanks in advance.


Sent from my iPad using Tapatalk

I towed with mine on day 2. IMO people overthink these things. 

  • Like 2

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share
Go to topic listing

  • Recently Browsing   0 members

    • No registered users viewing this page.

  • Forum Statistics

    250.5k
    Total Topics
    2.7m
    Total Posts

  • Member Statistics

    342,965
    Total Members
    8,960
    Most Online
    DaleB
    Newest Member
    DaleB
    Joined

  • Who's Online   4 Members, 0 Anonymous, 1,318 Guests (See full list)

  • Latest Articles

  • Posts

    • jgaudet99
      Tire psi

      By jgaudet99 · Posted

      Yes that's right, it's the upgrade that includes the overload spring and all that stuff.   Someday when I'm empty and going by a scale I'm going to stop in and get some weight readings.   Exactly  you should have the ability to change individual settings, in in Canada so I'm driving with kph but then I'm stuck with kpa when I want psi lol    
    • Chuck FB
      Tire psi

      By Chuck FB · Posted

      You must have that upgraded gvw package which is only available or at least was in 2025 with the diesel engine for the 3/4 ton and that gave the truck physically the larger 12.0 ring gear rear diff and the 3500 rear spring pack. There is a difference in what the diff housing looks like externally as one tell tale and also your truck should have the upper overload spring pack and the frame pads that the pack goes up against.    The pressure the tpms system kicks the alarm in on a stock setting truck, that is a good question and was just from what I recall but I doubt I made any notes on it as I knew for the rear that it was not at all what I was after regardless either. Being that you have a diesel and if running on stock tires the minimum pressure on an empty truck seems to be around 50 psi from hearing of those that have weighted the front axle but the rear axle is very similar in weight to a gas truck and again a near empty truck on the rear could go down to 35 pounds at minimum. However the weigh scale is the proper way to know for sure as a guide.    As to changing the readings on the dash from metric to the US measuring system, oh yes that is done easily but what I was attempting to explain was that I can't pick and choose items I want to have in US and those I still want in the metric system at the same time as its either all or none. For example lets say you drove into Canada and switched your dash over to metric so your speedometer read in km an hour, well then your reading kilopascals on your tpms readout and your wife looks over and says what the hell is that saying in the tpms screen and you say "darned if I know, I think its Chinese" !
    • Chuck FB
      Some Assembly is Required

      By Chuck FB · Posted

      This is partly why I decided to have switched over to Amsoil SS as a way of hopefully preventing the buildup of the sludge/carbon on the pistons and clogging of the oil control rings and the carbon that would cause the compression rings to stick in their grooves as well as stay cleaner up top of the heads in the valve train in the first place, an oil that has tested better by third party testing over typical shelf oil and also doing my best to run relatively short OCI. However in saying that I don't think there is any way to easily prove the oil I was using prior allowed for a buildup at the OCI I was doing, nor in the other direction to make claims the Amsoil is keeping everything clean either. There really isn't a window into the engine is there to know anything for certain even if oil samples were taken for example that showed still healthy oil being dropped out of the oil pan other than engine tear downs that extensive and expensive testing of oils does to actually visually see what is really going on inside the engine. I wish there was some easy method of seeing what is going on but I don't happen to be aware of that if there is.  
    • jgaudet99
      Tire psi

      By jgaudet99 · Posted

      My truck is a ¾ ton but my placard also says 80 for the rear tires, I think I might have the upgraded suspension to the 3500 series maybe.   I put my air down to 60 and the light was still on, and there was no way I was putting over 60 psi in the rear empty and not towing because I knew the actual number Toyo gave me and I didn't wanna ruin the center of my tires!   And you actually can change it in the settings from metric or is and it will show kph or mph then when you go into your tire settings it will be either psi or kpa, but it would be nice to just change it directly on the tire psi page 
    • Grumpy Bear
      Some Assembly is Required

      By Grumpy Bear · Posted

      Common Sense Assembly   Your driveline is forgiving of the occasional mistake. It will even often forgive the random serious blunder. But it will not forgive a continuous bad habit.      What? Not everything needs to be a five thousand word essay.       

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...