Classic car builders, racers and other enthusiasts will now be able to purchase a GM 6.6L L8T V8 engine block directly from Chevrolet Performance.
Chevy announced the addition of the GM 6.6L L8T V8 engine block to its official performance accessories catalog this week ahead of the start of the SEMA360 online trade show on November 2nd. The automaker says the iron cylinder block can serve as the “foundation for your direct-injected performance engine,” and also claims that it “may see more horsepower than a lightweight aluminum block was designed for.”
The L8T engine comes standard in the 2021 Chevrolet Silverado HD and GMC Sierra HD and is optional in the 2021 Chevrolet Express and GMC Savana utility vans. The 2021 Chevrolet Low Cab Forward 3500 and 4500 cab-over trucks also offer the engine as standard. The V8 serves as a replacement for the GM 6.0L L96 V8 and produces 401 horsepower at 5,200 rpm and 464 pound-feet of torque at 4,000 rpm in fully dressed production guise. It has a 103.5 mm x 98 mm bore and stroke and a 10.8:1 compression ratio.
Finished GM 6.6L L8T V8
This product is intended to serve as a foundation for engine builders, with Chevrolet Performance also offering a variety of other off-the-shelf production and specialized performance components to help customers complete the motor. The production version of the L8T V8 has aluminum heads, a forged steel crankshaft, forged connecting rods and variable valve timing.
GM also announced a new Electric Connect and Cruise package ahead of SEMA360, a turn-key electric powertrain with a 200 horsepower motor and 60 kWh battery. It also debuted the Chevy Blazer-E, a 1977 K5 Blazer that appears mostly stock and features this same Electric Connect and Cruise package. While Chevy may be looking to satisfy earth-friendly enthusiasts looking for a greener solution for their classic, the addition of the L8T V8 block to its accessories catalog shows it’s not abandoning traditional customers, either.
Subscribe to GM Authority for more GM L8T engine news and around-the-clock GM news coverage.
Comments
The significant difference between this new design 6.6 liter iron block and the outgoing 6.0 liter truck engine is that the 6.6 liter has small water jackets between each cylinder. This means under extreme loads running on gasoline or if you choose to run on LPG propane, the engine is less likely to over heat. Propane contains about 37 percent hydrogen and burns hotter than Hades, so the extra cooling design, means more consistent heat of the coolant in the engine and transmission fluids. The new design 8.0 liter big block was also designed with full water jackets so it can run cooler on propane. The 8.1 liter big block it replaced did not have full water jackets surrounding the 360 degrees of the cylinder. Too bad that GM ignored the ultra high output offshore boat racers who needed full water jackets on the LSX iron blocks. The cost savings of this 6.6 iron block compared to aluminum, will be at least $1,000 less, maybe more.
The iron block LQ4/LQ9/L96 6.0L’s have cast in water jackets between the cylinders, but the larger 4.065″ bore of the L8T didn’t leave much room between the cylinders for cast in water jackets. GM’s solution was to cast the 6.6L block with siamesed bores (no water jackets between the bores) and drill coolant passages in diagonally. This really is a great solution as it makes for a stronger casting and still provides cooling between the cylinders, which is of particular importance for commercial applications as Mark has stated above. The precise location of the drilled water passages should allow at least a .030 overbore without core shift concerns.
BTW- that forged crank out to be in the Performance Catalog too!
The fully counterweighted crank will be available soon. It was not available at press time
Thanks Bob, for pointing out the details of the drilling of a water jacket between cylinders, instead of casting it. I knew those facts, but i didn’t want to write a book about it in my comment above. This L8T block will be a great base for the short GM school buses that run on propane. California banned diesel school buses about 6 or 7 years ago. Since the L8T is lighter than the new design 8.0 liter big block LFI, and also physically smaller, it could possibly replace the base alternate fuel 8.0 liter LFI big block engine in the full size Freightliner school bus chassis. The factory compression ratio on the big block 8.0 liter LFI is 9.9 to one but on the smaller LS 6.6 liter L8T, the factory compression ratio is a much more suitable 10.8 to one, perfect for using 104 octane propane or 120 octane CNG.
I want to know if GM is doing anything about the fish bite problem with their 8 speed trans. my dealer has no clue and yes they have swapped the ATF twice
Try a performance aftermarket torque converter.
how bout the 9 speed trans that wont shift into 1st after coming to a full stop. or has the DIC that states to put the vehicle into PARK when it already is in P
Racing has become just a big money game now.I think going to a local track and watching your neighbors race is much more interesting.Like all sports I pay more for something if it is connected to commercial sports.Then again to each their own.I still wear my Pontiac hat and I had to pay for it.You would think the dealer would have gave it to me for all the Pontiacs I have owned since 1967.
Thanks Bob, for pointing out the details of the drilling of a water jacket between cylinders, instead of casting it. I knew those facts, but i didn’t want to write a book about it in my comment above. This L8T block will be a great base for the short GM school buses that run on propane. California banned diesel school buses about 6 or 7 years ago. Since the L8T is lighter than the new design 8.0 liter big block LFI, and also physically smaller, it could possibly replace the base alternate fuel 8.0 liter LFI big block engine in the full size Freightliner school bus chassis. The factory compression ratio on the big block 8.0 liter LFI is 9.9 to one but on the smaller LS 6.6 liter L8T, the factory compression ratio is a much more suitable 10.8 to one, perfect for using 104 octane propane or 120 octane CNG.
Another strong well engineered block from Chevrolet. I’m a retired engine builder and love to go camping, I tow with a 6.0 2500HD with over 300,000 miles, no complaints pulling a 5th wheel. It has been a great truck and it is well maintained.
In my days of racing I used various crankshaft and block combinations to come up with 355, 377, 383, and 406 engines. I’m looking for a good winter project so I have started looking at parts. However the LT8 has no parts as the parts system shows a choice for 6.6 gasoline but when i look for a short block there are only diesel parts. A LT8 short block will give me some more torque and all of the durability I want for a daily driver.
If you want even more cubes and torque at a lower RPM, just use an aftermarket 4.10 inch stroke crank. Leave the pistons alone, just change the rods and you will have 425.85 cubes or 6.9784 liters. One of the brand name forged cranks i checked out last week with a 4.1 inch stroke was listed for $921. The best thing about the piston bore size is that at 4.065 inches, GM makes a number of pistons that size in different compression ratios. This means even more aftermarket choice for racers with ring choice, etc.
Can someone recommend Off The Shoulder Tops? Cheers xx