PerKr

Cool. so there's a 2008 427 and a 2013 427. didn't know that.

lt4obsesses

It would be cool though. A big cubed, burbling V8 just behind your right shoulder. That would create a visceral driving experience. But alas, those days are long gone.

Quinten33

Racer X

No, not true, in terms of physical space required, or weight of the entire engine, especially including turbos and plumbing. Maybe if you were comparing it to the old iron block, iron head, "big block"427, but not compared to the LS7 "427".

RussM05

No argument from me.....I am a big fan of big displacement engines (although my daily driver is the ATS-V with the 3.6L V-6 twin turbo).

However, from the manufacturer's perspective...including fuel economy...they have moved on to smaller displacement and turbo engines. I doubt the LS7 (or version of it) will come back as a main-stream engine. Sorry..

RussM05

By the way, I asked the chief engineer for the ATS-V why they didn't make it with the LS7 and he just turned around and walked away. Must have heard that question 1000 times.

I must say the 3.6L Twin Turbo in the ATS-V makes plenty of power....the forums say it will make 500hp to the rear wheels with only minor mods. I believe them. However, the exhaust sound is no where near that of a big V8. I would love to have an LS7 in my car.

Zaro Tundov

The reason they used a one-off twin turbo V6 is because the worthless Cadillac executive Bob Ferguson wanted the ATS-V to have a "twin turbo six like BMW." You can bet your *** that the Chief Engineer of the ATS-V fought him on it, and that's probably why he didn't answer your question, because he couldn't tell the truth and he was sick of covering for Ferguson's dumb ***.

Why The Cadillac ATS-V Uses A Twin-Turbo V6 Over A Naturally-Aspirated V8

MitchAlsup

Do you have the data to back this up.

4.0 litre DOHC Twin Turbo occupy a larger volume than a 6.2 Litre, OHC LT motor, and can easily weigh more once you add the weight of the entire package together.
A great big motor turning over slowly gets better mileage than the little bitty motor revving its heart out.

lt4obsesses

True, the space consumed by the 7 ltr engine and the 6.2 is the same. The cubic inches came from boring out the cylinders and stroke. However, in so doing, the cylinder walls could not handle forced induction. That is why they used the 6.2 ltr in the C6 ZR1 instead of the LS7. Same principal as to why Dodge uses a 6.2 ltr in the Hellcat while the other SRT's get the n/a 6.4 ltr.

Forced induction is here to stay, at least until something better comes along. The C7 Z06 is testament to that, if they could've gotten a 7 ltr n/a engine to produce that kind of power and maintain economy and emission standards, they would've done it. The good news is that it is now driving the industry to improve these systems in terms of lag and thermal control. Just like 20 years ago the thought of a 750 HP production street car would've earned you a trip to the funny farm, 10 years ago the thought of a 600 hp V6 would've earned you a ticket on the same train.

JoesC5

The LS7 with it's 4.125" bore is not a LS3/9 block bored out from 4.060". The LS7 does not have .0325" thinner wall than the LS3/9.

In fact the LS7 is an entirely different block and is manufactured different than the LS3/9 block.

The LS3/9 block is cast with the iron liners in place, and then the liners are finished bored to 4.060" ID.

The LS7 block is cast without liners and then the aluminum cylinders are machined to size to accept pressed into place iron liners. The LS7 iron liners have both a larger OD and ID than the iron liners used in the LS3/9. The LS7's block has larger OD of the aluminum cylinder(resulting in a slightly smaller water jacket) and since the aluminum cylinders have a larger OD then the LS3/9, the OD of the aluminum cylinders are siamesed for additional strength.

Cliff noes: The LS7 does not have .0325" thinner cylinder wall thickness vs the LS3/9.

JerryU

It will be more like a 227! Hold on large cid V8 lovers the world has changed! The current EPA goal for a Corvette size sports car is 56 mpg in 2025. GM is also proposing to the government a compromise so they don't have to make special cars for CA! Expect it may get to 50 mpg but probably not much less! For every mpg less GM pays a financial penalty. Read that as "you will pay" and GM is unlikely to want too many cars/trucks that have to pay even if they pass the cost to the buyer.

If you haven't heard, the 2019 Silverado that is no doubt more profitable and sells 550,000 annually gets a turbo 4-cylinder engine in 2019! Yep it's hear! Now although it will produce 320 hp doubt some of the macho truck owners will be jumping and saying great! Yep the world is going to smaller, more efficient turbo engines that can use some of the ~30% wasted exhaust gas to gain efficiency. The smaller cid is less friction loss when cruising.

Just Sayn'- get ready!

PS: the Ford GT that is beating the current C7R is a 3.5 liter (213 cid) twin turbo V6 producing 647 hp! And that is not the race car engine, it's what you get if you buy one.

Zaro Tundov

The 4.2TT DOHC V8 wins on efficiency and power to weight ratio. The antique OHV V8 wins on packaging and absolute weight. I'll take the former over the latter any day.

lt4obsesses

Read numbers 4 and 5 under the History paragraph. The whole article is an interesting read.

https://www.corvetteactioncenter.com..._pursuit4.html

JoesC5

Are you also aware that Callaway offered a C6 LS7 Z06 with a blower with 652 horsepower and in it was engineered in conjunction with GM and had the full GM power train warranty plus the Callaway warranty on the supercharger.

I stand by my statement that the LS7 was not a bored out LS3 engine with .0325" thinner cylinder walls than the LS3.and GM had no problem warranting the LS7 with a supercharger with 652 horsepower as engineered by Callaway.

*89x2*

Nope. No. Not a chance.

JoesC5

The LS7 is a much more expensive engine than a LS3. The LS7 was designed for a higher end RPM to extract the target horsepower.

GM knew that forced induction could get the target horsepower for the ZR1 with a smaller displacement engine and save money as the same LS3 block that is used in the LS9 could be cast and machined on a automated transfer line along with engines bound for trucks, SUV's and Camaro's and base C6's, but not assembled in New York.

No need for GM to use a 7L engine for the ZR1 when they could get the target horsepower from a smaller cheaper 6.2L engine with the addition of forced induction.

That doesn't mean that the LS7 block was too weak for a 652HP(Callaway) or a 657HP(Edelbrock) supercharger installation, or for a 638 HP LS9/ZR1.

PS- the engine in the "race car" C7 R uses a LS7 block, with new pressed in iron liners(4.090" bore), and a shorter stroke crankshaft for 5.5L. That is a carry over form the C6. Even with the C6 R, GM chose to use the LS7 block instead of the LS3/9 block as a starting point for their 5.5L application..

The "weak link" in the LS7 are the cast pistons. They can handle the boost as long as it's kept under 5.5 PSI. With 5.5 psi boost the LS7 can make, and handle, 652/657 horsepower, but if one wants more horsepower than that, they need to go with forged pistons(like what is used in the LS9). When not in boost(as is the way the engine is run for CAFE), a higher compression ratio gives more torque at low RPM when run in NA mode( when at part throttle cruising at 65-70 MPH), resulting in improved gas mileage. That's why a C6 Z06 has better gas mileage than a C6 ZR1, as neither is run at WOT to get their CAFE numbers.
That's why a C6 ZR1 with smaller displacement 6.2L gets 21 MPG highway CAFE/EPA number(and a gas guzzler tax to boot) with a .5:1 6th gear and a honking 7L C6 Z06 gets 24 MPG CAFE/EPA number(highway with no gas guzzler tax) with the same .5:1 6th gear. and both with the same 3.42:1 rear gear.



Personally I like the higher compression ratio with lower boost as used in a LS7 with either a Callaway or Edelbrock supercharger than a lower compression ratio with higher boost as used in the LS9.

.

lt4obsesses

What the hell man? How did you do that? I deleted that post like an hour ago because I chose to be done with this conversation.

Michael A

Now that there is no hood clearance problem, time to look at an LSX tall block 454.

The LSX454 crate engine makes 627 horsepower. That would make a great base engine. There is also the LSX454R that makes 770 horsepower.

Kenny94945

Yes time to move to a 454 from 427 as we wean off 100% gas engines.

Michael A

If you they go out, they need to go out with a bang!