kcducttaper

So, story goes, I'm a n00b to these forums. I've wanted a 3rd gen camaro ever since I was like 10. Now that I'm getting close to graduating with a degree in engineering, I may have the budget to build one up before too long. Here is the basic "criteria", but it can be a little bit flexible if it seems a bit optimistic:

400-500hp (yes, I will swap for a stouter tranny - manual style)

30+mpg (or as close to it as I can get) highway

preferable 87 octane, but that doesn't seem too practical

0-60 comfortably less than 6 seconds, or even 5 (should be practical with that kind of HP and a good drive train)

smoke my dad's stock Honda S2000 (theoretical 0-60 in 5.4, but most people seem to get high 5's or low 6's in the real world) The S2000 really is a track car. I'll prolly tweak the suspension a little bit for the HP and some better handling, but for now, I'm just working on the power train.

I know you 'can' build up the 305 or 350 to that level, but that hardly seems worth it after you spend all the $$$ on parts. I've thought about finding a fairly new corvette or camaro that's backed into a tree really fast at a junk yard and snatching the ls3 motor/tranny from that and dropping it in. It seems like the newer aluminum 6.2 would weigh about the same as the old iron 5.0 or 5.7, so weight seems like it should be nearly identical. I like the active fuel management system on the 5.3 in my dad's truck, which seems to average about 23-25mpg when it's on 4-cylinders. I've thought about dropping that in as well, but I probably won't since I'll have to do a bunch of mods to get the HP out of that too. Somewhere I heard that the active fuel stuff only works on auto trannys. Is that true? Anyways, if you've got some good tips and ideas, send 'em on over.

vetteoz

iTrader: (13)

https://www.thirdgen.org/forums/ltx-...third-gen.html

kcducttaper

I read that, but it's not really answering what I'm after. That's mostly highlighting what a conversion to an LS1 motor would take. I'm still deciding what motor to stick in there, which may not necessarily be an LS1. I'm currently leaning towards the LS3, which is a derivative of the LS1, but it may suit my needs better.

InfernalVortex

iTrader: (4)

Phase 1: Find LS? motor
Phase 2: ????
Phase 3: Profit

???? will vary depending on what you start out with. You can make a 400hp 5.3 if you want. Or you can do it with an LS7. Just figure out what you can get for what price and use extra money to hit your power goal.

vetteoz

iTrader: (13)

It hi-lights the technical requirements for a LSX swap (vs a drop in old skool SBC)
You have to decide if you are up to or have the ability to do the LS swap?

watajob

iTrader: (29)

I'm a big fan of SBC1 engines but the only way you're gonna' get close to that mileage/power combo is LS. Although, IMHO, when you figure in the ancillary costs of an LS swap, (crossmembers, wiring harnesses, headers, etc), you can build a pretty stout old school engine.

1gary

Old gen I vs a LS??. Hands down a LS.Change the way you think about things.Don't compare what's"cheaper". Think about your goals and what you have to pay to get there. That's my advise.

kcducttaper

I'm not terribly worried about build cost and I'll be doing a vast majority of the stuff myself to keep cost down. I figure it'll take around $10k to make a decent build, and more like $15k or better to make a killer build, and I'm ok with that, but I do like to save a bit here and there when applicable. I'm just working on getting my ducks in a row so I don't have to waste time planning stuff when it comes time to build it. I know I've said this before, but I'm really liking the LS3 motor. 400+ stock, and pushing 500 with a bit of a cam upgrade is nothing to sneeze at. My brother and I could probably make something to imitate the active fuel management fairly easily to boost mileage.

Jim85IROC

iTrader: (2)

There is no AFM on an LS3. The L99 is the LS3 equilavant with AFM.

abray1

I have a 2002 LS1 corvette (3.15 gear auto) and it gets around 27mpg when driving it right. My old 89 350 auto iroc got around 24 with 2.77 gears. I vote for a ls6 if you don't go old school. I have a 92 vert with the same goal and I am going old school with a holley stealth ram and all forged 350 bottom end. I haven't decided on heads and cam yet but I am leaning toward brodix or fast burns with a custom cam. Probably get around 23mpg realisticly.

brando54009

ls series is pretty much your best bet. it takes quite a bit to get older motors to make that much and at that your stringing that motor out. you could do a pretty much stock ls with a good cam and some n2o and that will help you reach your goals pretty easily

1gary

Also.Break a really bad habit.HP don't mean squat on a street car.Torque is the deal.And the LS engines will get you there as well.

kcducttaper

Good call on the HP vs torque thing. These motors have a pretty good torque curve though which generally seems to keep up pretty well with the HP curve unless you've just got a really awkward cam in there.

So it sounds like everyone says LS is the way to go. I'll probably end up going for an LS3 (perhaps with a mild cam), or the L99 to get the AFM (provided you can use it with a manual - if not, ls3 it is). It really wouldn't be too difficult to route 4 of the injector wires through a little controller box that shuts them off if I'm going faster than say 42mph, and if my throttle is below 10%. I'm not terribly sure how well this would work for the engine and what any long-term affects may be since the valves are still doing their thing, but there's no power stroke. In theory, you'd get probably 60-75% of the power back from your compression stroke after you've lost some compression through the seals, and lost some energy to heat. It seems like it would give me a couple more MPG's on the highway without really harming anything. I'll have to do a bit more research on it, but it wouldn't be hard to make something like that.

DIGGLER

iTrader: (1)

a stock LS2 with 1.7 rockers, fast intake/tb, kooks headers/exhaust, and a good tune can knock down 30mpg in a 3900lb gto. 500 miles to the tank. made over 400rwhp and huge torque.

kcducttaper

Sounds promising. Didn't the LS3 replace the LS2 because it's more reliable and hits the same numbers? I thought I read something along those lines, but I can't quite remember now. I need more coffee.

Orr89RocZ

iTrader: (20)

You hear the stories on lsx cars making high mileage but mine aint one of them. Bolt ons with auto and 2.73 highway gears it get 25 best day. Mostly 24. My L98 got 22-23. Same gears. Mixed driving was abit less i think 20-21 with some stop n go. Not city driving or aggressive. Now with 3.73 it gets 18-19 mostly highway.
If i am hard on it it goes way down.

Friends auto heads cam gets 13-14 city and makes 430 whp.

I guess 6 spd cars are capable of more. Then again mine and my friends cars arent tuned for absolute best mileage.

But internet claims all state 30 mpg is possible. Guy from sts turbo claims his 800whp turbo vette gets something out of this world like 37 mpg. That i need to see

paul_huryk

You have two real options:

1) Go LSx in your car, which are proven to get good mileage, even with heavy mods

2) Go SBC (350 or so) with a proper H/C/I combo and aftermarket FI. Carb is going to drag the mileage down into the unacceptable range for you.

Also - while the transmission and gearing factor into the car's mileage, don't forget about weight and it's impact on gas mileage and performance. A 3000lb car with a 300hp engine will get better mileage than a 3500lb one with 350hp - even though both would be about equally fast at the track.

DIGGLER

iTrader: (1)

i rode in the 30mpg gto. took a trip from SC to Maryland and back on a single tank of fuel.
my camaro has a ls1 with ls6 heads/intake and a 233/239 cam. it got 23-24mpg hwy. i had an LT1 car with a 230/236 cam that got pretty much the same mpg.

1gary

Well here is a thought.With a properly tuned EFI and turbo needing racing gas big numbers in torque/hp,and soft peddling gas mileage could be had.Look at what NASCAR is doing in gas mileage with a EFI and no turbo and they are spinning those engines tons higher than we ever would.

Z28flash

I've also been very interested in a LS3/third gen swap.Another thing is can you go further with a 5.3,5.7 or 6.0 for the price of a LS3?
5.3's and LS1's are really cheap and a few grand can make the power of a LS3 and still have money left over.

kcducttaper

Well, after a ton of thinking it over, I'm pretty dead-set on the LS3. They have 400+hp stock (with a ton of torque as well), are just a mild cam and a bit of minor tweaks to punch out 500+, are just a super/turbo charger away from cranking out 700-800 or better. They get pretty decent mileage when you're driving them on the highway, they've got a ton of aftermarket parts easily accessible, and they'll last me quite a long time (supposedly).

Atilla the Fun

Now that the OP has the answer, I'll point out why this is not correct. EFI forces you to cruise at stoichiometric, while a good Q-Jet can cruise much leaner, while still supporting 400 real HP. To get 400 real HP and 30 real MPG from a 350, you'd have to use perfectly-ported Vortec heads with the very best-flowing 1.94 / 1.60" valves, a surprisingly modest HR cam, and an Extrude-Honed GMPP EGR ( Performer ) intake manifold. Gearing would have to be between 1700-1900 at 65, and cruising speed NO faster than 65 MPH. This would require a lowered T/A on tires NO wider than 245s. Getting the 350 to either 30 MPG or 400 HP is easy. Getting both at once is the issue.