Generation IV Internal Engine - 400hp build, ls1 or ls2 for mpg?

I have a basic question. If one were to build an engine to 450hp at the crank, would you get better gas mileage from a ls1 or ls2? If bigger displacement is what i want, would I go with the ls2 or a stroked ls1? If smaller displacement is what i want, would I go with a destroked ls2 or a ls1.I'm aiming for a smooth curve and not peaky since this car will be a road racer. That also means no turbo or NOS.

Ls2 theres no replacement for displacement.

The mpg between the two is minimal. The mods and cam etc are really going to determine your mpg along with tranny and gearing.

There has to be a difference from the engine designing standpoint. If all I wanted was power, then yes the ls2 would be perfect. But all I want is 400hp, there has to be a best way to get there. If it makes a difference of 1 mpg, that's worth my time to figure out. I'll get the gearing and the rest right once I get there.

build a Gen4 5.3 with VVT for the best results.

Well the ls2 is gonna put you way closer to the 450 hp than the ls1 and wont take as many mods, and still the mpg difference between the two is negligible

The LS2 engine would be able to do that easily with just bolt ons without touching the engine. The LS1 would need a medium cam along with the same bolt ons.

Given that, I would go with the LS2. It's easier to get the power you want, and it would undoubtedly get better mileage due to having the stock cam vs. a bigger aftermarket cam in the LS1.

I would be that the amount of money you are willing to spend will make a larger difference in overall MPG. The best heads, intake, and exhaust will all add more power than "budget" parts without making a huge difference in MPG (I actually gained mpg with headers). I'd say an LS2 with quality heads/intake/exhaust plus a mild cam would get you to your goal with reasonable street manners, good power throughout, and "good" MPG.

More cubic inches will equal more torque for less effort (milder cam/heads, etc.). Torque is what will move the car down the road when you're cruising. The less the engine has to work to maintain speed in your vehicle, the less fuel it will use. Then it goes back to transmission, gearing, weight, etc. You are only talking about less than 20 cubic inches so it's not a real night and day comparison.
Also factor in that LS2s are MUCH more expensive than LS1s, may not end up being worth it.
The body of the car will have a dramatic effect on what type of mileage you're gonna see of course. A C5 is going to be a lot more aerodynamic (not to mention lighter) than a 69 Chevelle.

Can Variable valve technology and active fuel management or Displacement on demand be put on a ls1? Is that only technology for the 5.3L and 6.0L? Could someone put those systems on a ls1 or Ls2 that originally didn't have it?

Can Variable valve technology and active fuel management or Displacement on demand be put on a ls1? Is that only technology for the 5.3L and 6.0L? Could someone put those systems on a ls1 or Ls2 that originally didn't have it?

A lighter car and more efficient drivetrain would go much further in the saving of gasoline than the addition of DOD which is only shown to improve MPGs by less than a handful on the highway.

I have the l76, ls2 with l92 heads and AFM or Dod. It sucks, dont use this shit.

The LS2 would be the better choice. My reasoning is that with less displacement, you'll have to make up for that with a more agressive cam. More agressive cam, means more overlap (tighter LSA), and that KILLS MPG.

Also look at the C6 ZO6 compared to a heads cam f-body. Both can put down 450rw but the f-body will do it while getting 5 MPG worse in the city.

Ported heads and a z06 cam will easily net you 410-420 at the wheels with an ls2!

Easiest thing is to just buy a new LS3 crate engine!

The OP did mention about road racing...so I'd imagine he may want a higher
power band (shift point) than perhaps a stock cam can provide.
Also knowing that roughly 60% of an engines rotating friction is the piston
rings so an LS1 @ 3.898" bore will have less ring surface area than the 4.0"
LS2....splitting hairs I know but bear w/me hear. Yes vehicle weight, shape,
gearing, trans type, all play important roles in MPGs but I want to focus on
the engine side. Cylinder pressure (not static, but cranking compression) is
very important to engine efficiency. Maximizing this reduces the BSFC.......
Brake Specific Fuel Consumption. This is the number of pounds (per hour) of
fuel required to support each horsepower the engine makes.
Point made is you can mill LS1 heads (say .020-.030), use thinner than stock
head gasketss (which tightens the quench clearance) and run a smallish
(218 -226 duration) cam with a wide 115-117 lobe separation that will idle
and run like a stocker but give you a broad powerband 2500-6500 rpms yet
still knock down excellant fuel economy.

LS6 block 243 heads with a mild cam. I'd go with a 224/224, it will get 450hp with ease and a nice broad tq curve. You could possibly do it with a LPE GT2-3 which is even milder with all the bolt ons.

Road racing, the LS6 has the best ventilation and if you read or hang out around the Corvette track guys/T1 racers, the LS6 block was the most reliable.

My Futral F11 228/230, TEA Stg 2 5.3s stock LS6 intake polished stock TB did 29-31mpg on the Hwy on 3.42s/M12 at 75-80mph

All lsx blocks after 2005 (ls2 style and up) have the bay to bay breathing which was the only difference between ls1/6 blocks


Just get a damn ls2!

All lsx blocks after 2005 (ls2 style and up) have the bay to bay breathing which was the only difference between ls1/6 blocks


Just get a damn ls2!

True but that doesn't mean the Ls2 is as durable while road racing.

http://forums.corvetteforum.com/autocrossing-and-roadracing/2824807-let-me-ask-another-way-whos-ls3-hasn-t-blown-up-on-the-track.html

No need for a LS2 at 400hp. The bigger bore will be sucking in more air and thus harder to get the mpg while cruising.

True but that doesn't mean the Ls2 is as durable while road racing.

http://forums.corvetteforum.com/autocrossing-and-roadracing/2824807-let-me-ask-another-way-whos-ls3-hasn-t-blown-up-on-the-track.html

No need for a LS2 at 400hp. The bigger bore will be sucking in more air and thus harder to get the mpg while cruising.

4 vs a 3.9 bore. If you even notice a measurable mpg difference on identically built motors, it would probably be so small as to be statistically insignificant.

Lots of fair dust and unicorn chasing in here. Driving habit and tire pressure will far outstrip anything that a difference between a LS1/6 or LS2 will.