The new 6.6L V-8 GM engine for use in the all-new 2020 Chevrolet Silverado HD and 2020 GMC Sierra HD has been assigned RPO Code L8T, GM Powertrain’s Tom Read confirmed to GM Authority.
The L8T is a new gasoline engine for use in Heavy Duty pickups. It displaces 6.6 liters in a V8 configuration via an OverHead Valve (OHV) layout otherwise referred to as push-rod. GM tells us that the motor is based on GM’s fifth-generation Small Block engine architecture initially introduced by the 6.2L V-8 LT1.
In the 2020 Silverado HD and 2020 Sierra HD, the new L8T GM engine makes an SAE-certified 401 horsepower and 464 pound-feet of torque, with strong performance at low rpm, where it is needed when pulling away with a loaded cargo box or trailer.
The 6.6L V-8 L8T gasoline engine serves as the base motor in the trucks, while the 6.6L V-8 Duramax L5P turbo-diesel serves as the optional up-level engine. The L5P makes an SAE-certified 445 horsepower and 910 pound-feet of torque.
So going forward, we can refer to the new 6.6L gasser as the L8T. Simplicity for the win!
Stay tuned to GM Authority for more information on the L8T GM engine, as well as for more GM news coverage.
Comments
I think it might be based on the Vortec 6.0. If you add a 4 inch stroke to the 6, you get a 6.6L V8. Corvette Racing has a similar setup where they added direct injection to the LS based engine. I think GM knows that the LS 6.0 was very durable and are trying to get the best of both worlds.
4.06 bore 3.86 stroke 400CID.
Are these the actual specs or are you just guessing as well? Im really curious to see more info on this thing. It took me awhile but i finally found at what rpm the peak torque was at. Motortrend broke that its 464 ft/lb @ 4000rpm.
I’ve been curious about how GM is going about achieving this displacement as well. Using a modern 4.065″ bore block seems likely, but 3.86″ seems like a bastard size stroke. Using a 3.875″ stroke gives you 402 ci’s and 6.6L.
I think a 402 ci motor with a 4″ stroke would be awesome though. A 4″ bore and stroke combo tends to make for good motors. LS7 uses a 4″ stroke. I’m not that knowledgeable about the newer LTx motors, but if I’m not mistaken aren’t the blocks and internals similar? Can you use LS cranks/rods/pistons in the new LTx blocks? I know the fuel systems and tuning is very different in them.
These are the specs. Go to
http://gmauthority.com/blog/gm/gm-engines/l8t/
YOU NEED TO READ THE ARTICLE AGAIN. IT’S BASED ON THE 6.2 LT1 ENGINE ORIGINALLY IN THE 2014 CORVETTE..
THE NEW 2020 HD PICKUP TRUCK 6.6 LITER ENGINE, IS NOT BASED ON THE 6.0 LITER. IT’S A STROKED 6.2 LITER. BOTH HAVE THE SAME 4.0649 INCH BORE. THE 6.2 LITER HAS A 3.622 STROKE, THE NEW 6.6 HAS A 3.858 INCH STROKE. USE A CALLIES STROKER CRANK OF 4.1 INCH, LEAVE THE BORE THE SAME AND GET 425.83 CUBIC INCHES, WHICH IS 6.9 LITERS. A CHEAPER OTHER BRAND OF CRANK OF JUST A 4.0 INCH STROKE GIVES YOU 415.44 CUBIC INCHES WHICH IS 6.8 LITERS.
Alex – what does this mean: “…the an OverHead Cam (OHV) layout otherwise referred to as push-rod…”
It meens that gn athoretie need too higher a prove reeder.
Yes, we proof read. But sometimes things slip by.
In any event… fixed and crisis averted.
Alex: You are the founder of GM AUTHORITY. Please note that making critical typos on a breaking story, correcting them only 18 hours later – and then making flippant comments about your error serves to dilute the brand that you founded and built for almost two decades.
Nota Bene: This was the second such editing error on these pages in two days.
Tomko, thank you for reminding me of the firm that I founded and in which I spend a dozen hours a day. Did you think this slipped my mind in some way?
Now, the error was fixed and addressed (much faster than your 18 hours calculation, by the way). What more do you want?
Some asides:
1. Most other publishers, editors and/or authors on other publications do not even notice or fix their mistakes… let alone read the comments and interact with their readers, flippantly (your perception) or otherwise.
2. The flippant tone of your comments makes it clear that the sense of entitlement is strong with you. We addressed the issue at hand… so I ask again, what else would you like – an apology cake hand-delivered to your doorstep?
3. What you fail to understand is that we do our very best to deliver timely and accurate information, day in and day out. Unfortunately, despite our best-laid plans and intentions, errors sometimes slip by now and again. So I invite you to take a step back and consider the human element involved in our work before turning the a$$hole switch to the next level.
4. There was a better, less flippant, way for you to handle this situation: simply head on over to our Contact page and let us know about the error there.
Sincerely!
Alex
I’ve seen Alex’s automotive presentations when he worked at GM and let me tell you, he’s a straight shooter with upper management written all over. He will go far in this industry.
One of the things that I appreciate about him is that he isn’t afraid to tell anyone how it is without the need to sugar coat it which is more than I can say about the head of any other publication… or about anyone else who worked at GM when Alex was there. He was the only one who would give us a direct straight answer without the BS.
As for the typo… I saw and it anyone with two brain cells would have understood that it’s a typo and that there is no need to make a big fuss about it. tomko obviously has issues and wanted to go after someone because of them. Looks like he went after the wrong guy and got told what’s what by Alex. Haha
Alex – keep up the good work. You won’t make progress without making a few enemies along the way.
A simple “I apologize for my mistake” demonstrates responsibility and professionalism.
You need to reread the article, it’s Overhead Valve not overhead cam
To understand the comment and direct quotation you need to read the article as it was originally published.
Would’ve named i L8R. as in later. as in “see you L8R, Ford, Ram”
Do you think this article is hand written? It clearly does not make sense. “the an OverHead Cam (OHV) layout otherwise referred to as push-rod” At least read over what you post. You would understand if you knew what you were talking about.
Excited to hear this beast on the road soon.
Iam happy gm has finally step up to the table to battle
The other two iam still looking at the video of the new Hd but I was expecting better numbers out of the new gas engine
With 464 ft/lb torque at 4000 rpms, it should have a similar torque curve to the 8.1L V8 but with a lot better fuel economy. And i never heard anyone complain about the pulling power of an 8 liter.
Just when you thought the Pontiac Aztec was the world’s ugliest vehicle, gm entered this front end to beat it…..you couldn’t pay me to be seen in that cinder block bug eyed design.
You didn’t mention the Nissan Juke as one of the ugliest vehicles. Looked similar to the Aztec but every always mention the Aztec..The Juked looked like a close cousin. Thank goodness the Juke has been discontinued.
The Nissan Cube made both of them look gorgeous
It’s a gen 5 motor with a cast iron block. Not much different then how the ls1 was rolled out then we got the ly6. If anyone thought the first gas motor would be more than a base camaro ur insane. Give it a few years and it will be 450hp 500lbft.
I’m very excited that after 13 years GM will finally have a really powerful gas engine option again. What I’m a little disappointed by is that again, it isn’t an 8.1 type engine, and it’s not going to be what the 8.1 was.
The 8.1 was and is special because it was much more powerful than the small block, but also because it used the same transmissions and drivetrain parts as the Duramax.
As for the power. The L8T is not the “new 8.1” or “next 8.1”. It is another small block, the difference is that it finally reaches power levels the that should have been being approached for years.
It doesn’t have the Allison, and it won’t beat the 7.3L Ford in power, and most likely not in transmission performance either.
I have believed for a long time that GM is long overdue to bring another big block to market, using the Duramax’s drivetrain and with over 500 ft lb torque. Ford got the right idea. Maybe 7.4 would be a good, also historically significant displacement number to shoot for.
Now the L8T.
Best GM truck small block ever? Just might prove to be.
Big block replacement? Hold your 401 horses.
Im just saying it will be close to the low end power That the 8.1L had. I would love for them to use the LSX454 block and build it as a truck engine. I might just have to do that myself
I wasn’t referring to you, just responding to comments I’ve seen elsewhere on social media. You’re right about the power, it should be like the 8.1’s low end at least.
HERE IS THE LINK TO THE REPLACEMENT BIG BLOCK COMPLETE ENGINE 8.0. IT WAS DEVELOPED BY THOMSON AUTOMOTIVE UNDER CONTRACT TO GM, BUT NEVER INSTALLED IN ANY GM TRUCK BECAUSE GM STOPPED MAKING THE MEDIUM DUTY TRUCKS IN 2011. JEG’S SELLS THE BARE BLOCK FOR JUST $902. LINK TO 8.0 LFI
https://gmpowertrain.com/engines/8l-lfi.html
Ive been a loyal GM customer for 30 years. Ive owned 6 new and 4 used GMs. I, and nobody in my family, will buy another GM product as long as BARRA is CEO. Good luck in China you SELLOUTS.
You’re off your meds today aren’t you lil buddy?
He is just doing what any consumer can do and voting with his wallet. There are probably several million folks out there with similar sentiments towards GM and Mary Barra right now.
Too bad it will be attached to a Ford transmission.. I will keep my bulletproof 2013 L96 backed with the untouchable MYD. You can keep your extra HP, torque and Ford parts.
Not true at all
It’s not a Ford transmission. It is a GM transmission 6L90.
Glad to here Stan say Ford transmission even though it is and has always been a joint effort from both Company’s. I would be upset if I wanted to buy a Chevy and their was no 10spd. But alas Ford is coming to the table with a 7.3 V8 gasser with the 10spd this fall looks like Chevy has dropped the ball again – build cheap and sell high ‘Chevy Motto’, all the time making the Chevy follower’s believe they are getting what they are paying there hard earned money for.
Read the article slowly. The new 6.6 L8T gas engine is based on the 6.2 liter, LT1 . This means it’s still a GEN 5 LS engine. This also means that different heads can be used, maybe even the LT! heads, for more flow and power. It will run great on propane becuase there are mini water jackets between each cylinder, even though it has siamese cylinders. Propane is very high in hydrogen content and they run hotter than hades. That is why GM developed a new big block 8.0 to replace the old 8.1 liter. They only shared one part. The big difference is that the 8.0 had full water jackets and the 8.1 did not. The 8.1 has siamese cylinders and they run too hot when using 105 octane propane. Thomson Automotive did all the development and testing on the 8.0 for GM. I used to consult with him and the GM engineer on Fridays for the weekly update. I ran propane for 25 million miles in three different fleets, so i know a thing or two about using it in commercial service. So, i’m happy that this L8T has small water holes between each cylinder to avoid overheating under heavy loads and when on propane. To get 425.93 cubes, just add a 4.1 inch crank. Don’t mess with the bore, keep it simple. That will mean a 6.3 percent increase in power plus another 2 to 3 percent for the stroke, or 503 lbs feet of torque and 435 HP with the same cam. Run a hot cam and get another 7 percent power over those figures or 465 HP and 538 lbs feet of torque. Ready Freddy.
6L90 sure is a GM transmission and a good one too!
Which brings me to this question?
How can a transmission CO-DEVELOPED by GM and Ford be called a FORD transmission? It was CO-Developed.
And didn’t GM own Allison Transmission ( the company) for many years? Would you not think that the new Allison “branded” 10 speed built “in house” at GM would not benefit from the fact that Allison and GM was essentially the same company for many many years?
I forgot to ask a very important something. Any news about this motor making it into the Silverado medium duty trucks? I think it would serve well at least in the 4500HD and 5500HD. The V10 Ford with less power in a F-550 dump truck I drive does very good in that size.
Yeah they are planning on offering this V8 in the medium duty.
Never again Dodge for me MAGA
I think it is great that GM has got back into the Medium Duty truck business. I would love to own a 2018 6.6 Duramax L5P Crew Cab Dually. Looking back I should have started to save up 9 years ago had I realized trucks would be so highly marketed. News of a 6.6 Gas V8 sounds great. I currently own a 2018 Silverado 5.3 Z71 Crew Cab.
Chevy/GMC are back to selling medium duty trucks manufactured by Navistar (International). I wish International would start making class A motorhome chassis since they also bought Workhorse from GM.
LINK TO REPLACEMENT BIG BLOCK MEDIUM DUTY TRUCK ENGINE THAT WAS NEVER FACTORY INSTALLED IN ANY PRODUCTION TRUCK JUST A COUPLE FOR ROAD TESTING, DEVELOPED UNDER CONTRACT TO GM BY THE OLD, NOW DEFUNCT, THOMSON AUTOMOTIVE IN 2009 AND 2010. THE OLD 8.1 LITER DID NOT HAVE WATER JACKETS BETWEEN EACH CYLINDER, BUT THE REPLACEMENT 8.0 LFI, WAS DESIGNED TO RUN COOL ON 105 OCTANE PROPANE SO IT DID NOT HAVE SIAMESE CYLINDER BUT FULL WATER JACKETS BETWEEN EACH CYLINDER. BUY THE BARE BLOCK 8.0 FROM JEG’S FOR JUST $902. NOTICE THS SHORTER STROKE ON THE 8.0 OF ONLY 4.25 INCH COMPARED TO THE 4.375 OF THE OLD 8.1 LITER WHICH WAS 496 CUBES. LINK HERE IS THE LINK TO THE REPLACEMENT BIG BLOCK COMPLETE ENGINE 8.0. IT WAS DEVELOPED BY THOMSON AUTOMOTIVE UNDER CONTRACT TO GM, BUT NEVER INSTALLED IN ANY GM TRUCK BECAUSE GM STOPPED MAKING THE MEDIUM DUTY TRUCKS IN 2011. JEG’S SELLS THE BARE BLOCK FOR JUST $902. WARNING, ONLY ONE PART OF THE NEW DESIGN 8.0 BIG BLOCK IS SHARED WITH THE OLD 8.1 LITER. EVEN THE FIRING ORDER IS DIFFERENT, LINK TO 8.0 LFI https://gmpowertrain.com/engines/8l-lfi.html HAVE FUN.
OMG turn off your caps lock and use some punctuation!
The grill of that truck is butt ugly! I can’t buy a bigger motor if the truck looks like that..
OK, PAY ATTENTION. The new 6.6 gas engine code L8T for the HD 2020 GM pickup trucks is the exact same bore as the 6.2 liter L86 pickup truck engine. It’s 4.0649 inch bore which is 103.25 mm. This means that the new 6.6 is basically just a stroked 6.2 liter. The 6.2 has a stroke of 3.626 inch or 92 mm. The L86 has a higher compression ratio, at 11.3 to one, to give 460 lbs feet of torque and 420 HP. The new LS 6.6 engine for the 2500 and 3500 pickup trucks for 2020, has a lower compression ratio of 10.8 to one. Here is the real deal, raise the CR on the new 6.6 to the same as the 6.2 liter L86, use the same L86 hotter cam and with the longer stroke of the new L8T, you will have a 6.3 percent increase of the stroke or inversely a 6.3 percent increase of power. This means the torque will increase on the L8T from 464 to 493 lbs feet of torque. The HP will jump from 401 to 426. But add another 2 to 3 percent to to each of those torque figures because of the effect of the longer stroke. This means the technical figure of 493 lbs feet will now be between 502 to 508 lbs feet on the dyno for the L8T, with the exact same cam and compression ratio as the light duty 6.2 liter L86 pickup truck engine. The HP increase because of the longer stroke is not as significant as the torque increase. Run it on E85 gasoline and expect another 6 to 7 percent in power according to GM published figures and the L8T 426 HP with the higher CR and hotter cam, will be at least 452 HP and torque will be about 539 lbs feet. Remove the normal cooling fluid and replace with the NASCAR coolant and add another 2 percent or 461 HP and 550 lbs feet of torque. But add an aftermarket crank of 4.1 inch, available from Callies and get another 6.3 percent in power or 490 HP and 585 lbs feet of torque. Add 115 octane racing gasoline and get even more power. All this without increasing the bore size, keeping it simple and the costs low.
The 6.6 doesn’t seem to be much of an improvement over the 6.2.
They’re going for low end power and better durability rather than all out horsepower gains.
401 HP/ 464ft-lbs sounds like a torque monster. It has a wider torque curve than old 6.0 as well
I think they mostly needed the steel block for the heavy duty pulling.
THE NEW 2020 HD 6.6 LITER IS BASICALLY JUST A STROKED 6.2 LITER. THEY HAVE THE SAME 4.0649 INCH BORE. BUT, SINCE THE BASIC LS SERIES CAN BE STROKED TO AT LEAST 4.1 INCH ( CALLIES CRANK ), THEN PUT A 4 INCH OR 4.1 INCH CRANK IN THE 2020 NEW 400 CUBE ENGINE AND YOU HAVE 425.83 CUBIC INCH WITH A 4.1 INCH CRANK. USE ONLY A 4 INCH STROKE AND YOU HAVE 415.44 CUBES. THAT’S THE SAME AS 6.80 LITER WITH THE 4 INCH CRANK. IT’S 6.9 LITERS WITH THE 4.1 INCH CRANK.
Somewhere I can hear Tim the Toolman Taylor saying “oh ohh ohh oh ohhh” Can’t wait to drive one of these trucks.
Curious to see how this is going to match up with the upcoming Ford 7.3 or the 7.0 Hemi. I fear GM kind of went a little small on the displacement here given the target market.
With that statement is GM doveloping a new big-block on thier own?.