Will an LS1 get better gas mileage than my sb400?

[Hazieview]

I was wanting a way I could turn my '81 into a pretty reliable everyday driver that wont break me. The best route I can think of is to by something like an LS1 out of a camaro or something. You will still have the power but it will do better on gas than my sb400/350th setup. Right or no?

The way I see it my '81 is way lighter than a 98-01 camaro (i think)
These camaros get around 17 in town and at least 29 on the highway (I know because my girlfriend has one). So an engine with that much power in a lighter truck should do a little better right?

My whole reasoning for this is I like my truck and it is payed for. Spending 3-4 grand on an engine is way cheaper than buying a new truck that still sucks on gas and doesn't have as much power as I have now. Plus it's custom.

What do you think?

(by the way my 2008 crew cab chevy gets 18mpg bst 16.8mpg average...)

[kainzien]

I really love my ls1/4l60e in my 81 swb. I haven't had a speedo unit last week so I haven't been able to get the gas mileage. I took a roadtrip to houston from Nac. (about 2 hr. drive) I filled up before I left drove to houston went out on the town that night, then drove to conroe the next day for gatordrag and back to nac. on a tank of gas. I drove it to houston again for texas showdown, and had no problems.
I would figure at least 16mpg. also the truck runs badass, the motor is basically stock except for headers, cia, de-screened maf, and a ported tb.
I would highly recommend the swap.

[Captkaos]

If you are keeping the EFI, most definitely yes over a Gen I SBC.. You could get a LS out of a pickup for less also.

[Hazieview]

So what would be my best bet for the swap?

What kind of vehicle should I be looking to get the engine from? Considering what the price range is and what would actually do what I'm wanting it to do? (Haul ass but still get more mpg than my sb400)

How much is it to rebuild the LS engines?h

I'm just worried about buying an engine and then have it blow up on my in a few months. Man that would suck...

[LMDGUY]

couldnt you add efi to the 400 and a overdrive trans. for less then doing a LS swap?

[Hazieview]

Good question and very good point. That is what I would rather do from the get go but I dont think it will be near as efficient but I dont know.... Also If I bought one perhaps I could put it on another engine if I ever happen to blow my 400. What do you guys think?

[Pyrotechnic]

Originally Posted by Hazieview

The way I see it my '81 is way lighter than a 98-01 camaro (i think)
These camaros get around 17 in town and at least 29 on the highway (I know because my girlfriend has one). So an engine with that much power in a lighter truck should do a little better right?
What do you think?

Your truck is a little heavier than the Camaro. Don't forget that the Camaro is like a bullet through the air, whereas your truck is like a giant box. It will get good mileage, but don't expect it to beat the Camaro, especially on the highway. You could expect high teens in the city and low to mid 20's on the highway, those are my estimates.

Forget about F-Body cars for swap engines unless you want to rebuild. They haven't been made since 2002.

Start looking at the 5.3L and 6.0L truck engines if you want to get a swap package. These are plentiful in junkyards and a complete drive train can be had for a reasonable price. The 5.3L will get the best mileage. You will need the matching 4L60E or 4L80E transmission, other wise you will be back to square one getting bad gas mileage.

[Captkaos]

Not around here you couldn't.
My brother picked up a low mileage 5.3L with all the accessories for his truck (no harness or computer) for $800, they had 20 of them. He replaced it this time last year with a 6.0L that came with the harness, wiring and ECM along with all the accessories for $1200. There is no way you could touch a EFI setup for $1200 AND get a motor with it. Another buddy with a 72 pickup got a 4.8L/4L60E with everything for $1200 and 8000 miles on it.

[chevymotocross]

What about a TBI 383 stroker? I've seen these around somewhere. They utilize the GM electronics and throttle body injection. Or even a TBI 350 which I bet with some mods, should make as much power as your 400 with better economy and efficiency. Probably easier swap than the ls1

[LMDGUY]

Originally Posted by Captkaos

Not around here you couldn't.
My brother picked up a low mileage 5.3L with all the accessories for his truck (no harness or computer) for $800, they had 20 of them. He replaced it this time last year with a 6.0L that came with the harness, wiring and ECM along with all the accessories for $1200. There is no way you could touch a EFI setup for $1200 AND get a motor with it. Another buddy with a 72 pickup got a 4.8L/4L60E with everything for $1200 and 8000 miles on it.

wow those are really good prices..I may have to do some shopping around for the next peoject

[N2TRUX]

Coulda, shoulda, probably, maybe?

Guys you are throwing out possible scenarios that you don't really know if it is a viable solution or not. The question asked is "Will an LS1 get better gas mileage than my sb400?". The answer is yes, much better mileage if you include the OD transmission in the swap. Even without the OD tranny, the GM EFI is much more efficient than a typical carbed set up.

Like Capt Kaos said, the cost of LSx based conversions have come way down. It is virtually impossible to beat by trying to hodge podge together a xxxci motor with brand xyz's efi system. In most cases the efi alone will cost you what you would spend on a complete LSx package.

[wildmanaaron]

And not only that, the ease, reliability and functioning of an LS based engine is a WHOLE lot more simpler than either a TBI engine (that you never can get to running 100%) or an aftermarket Edelbrock or Holley EFI system that is never going to be running as good as a 200K mile LS engine.

I WILL NEVER GO BACK TO CARB'ed engines unless its a completely original vehicle.

[Cherub]

Originally Posted by Captkaos

Not around here you couldn't.
My brother picked up a low mileage 5.3L with all the accessories for his truck (no harness or computer) for $800, they had 20 of them. He replaced it this time last year with a 6.0L that came with the harness, wiring and ECM along with all the accessories for $1200. There is no way you could touch a EFI setup for $1200 AND get a motor with it. Another buddy with a 72 pickup got a 4.8L/4L60E with everything for $1200 and 8000 miles on it.

damn i want to shop where you live

[Thumpin455]

The F body was around 3400lbs factory, my 98 Formula is 3300lbs. I doubt your 81 is much lighter if at all then my 76, and my 76 is over 4500lbs. No air, short box and only power steering for options.

You dont often need to rebuild the LSx engines, most F body guys start racing them when they have over 100k on the clock. Just plug em in and go, easier said than done yes, but you dont need to rebuild them like a SBC you pulled from a junkyard.

IMHO a 6.0L in either L92 or LQ4 flavors, with either the 4L60E or the 4L80E transmission they came with, and one of the stand alone harnesses would be perfect for your 81. A cam swap and a set of headers in an L92 is a 500hp engine that will idle better than your 400sbc, drive like a new car, and get much better mileage while doing it. Drop to a 3.42 gear or a 3.08 gear and you will see an improvement in mileage over 3.70 or shorter gears. Lower revs with the lock up converter and EFI with plenty of torque on the bottom will use less gas per mile traveled.

A 5.3 is an engine that you can almost get for free, there are tons of them, they make decent power and get good mileage. You wont be paying $6000 for a 5.3 and transmission, or even that for an LS1,LQ4,L92 either. The truck stuff is cheap and readily available. GM made millions of these engines, just like the 350 and 305, while they arent as easy to find and afford as a 305, they arent impossible or made of unobtainium.

Its worth it from the standpoint of drivability, power, economy, emissions, and longevity to put in an LSx engine. I am passively looking for L92s, for my trucks and for my 98 Formula, they make more power than my 454 does and drink a lot less gas in doing it.

If you are only doing it to save money on gas, well drive less, walk more, get a mountain bike, or pick up a $500 v6 or I4 beater.

[Hazieview]

Well thanks for all the input. I've never attempted a swap like this but I would love to try. I found this article I read very intersting.

http://www.superchevy.com/technical/...age/index.html

It's all about what you want to make of things. You can spend a lot of money and make one beast of an engine. I could also spend a little less money and still out perform my setup I have now and get better fuel milage at the same time.

I think we discussed almost every apect of what I could do. So it's coming down to what should I do.

What is the most cost effecient swap I can make and still achieve more power and better economy than my setup?

It sound like the 6.0L would be more expensive and harder to find than the 5.3L Correct? Even still would it be worth getting the 6.0L over the 5.3L?

Let's break it down to engine performance and pricing.

Thanks again guys!

[suicide 63]

Originally Posted by Captkaos

Not around here you couldn't.
My brother picked up a low mileage 5.3L with all the accessories for his truck (no harness or computer) for $800, they had 20 of them. He replaced it this time last year with a 6.0L that came with the harness, wiring and ECM along with all the accessories for $1200. There is no way you could touch a EFI setup for $1200 AND get a motor with it. Another buddy with a 72 pickup got a 4.8L/4L60E with everything for $1200 and 8000 miles on it.

Yea around here a truck 5.3l 4l60 combo with 60-70 thousand miles goes for 1300 to 1500 complete pull out. This is the only way to go in my mind when my engines get tired.These engines are rated at 295 hp.

[Pyrotechnic]

Originally Posted by Hazieview

What is the most cost effecient swap I can make and still achieve more power and better economy than my setup?

It sound like the 6.0L would be more expensive and harder to find than the 5.3L Correct? Even still would it be worth getting the 6.0L over the 5.3L?

How much power is your SB 400 making right now ? Is it a stock smogger ?

Both the 5.3L and 6.0L will get better mileage and make more power than a stock smog 400.

Newer regular cab short bed trucks with the 5.3L, 4L60E and 3.73 gears with 30" tall tires are capable of mid 14 second 1/4 mile times with just intake, exhaust, and a PCM tune.

To put things in perspective, the 5.3L is a 325 cubic inch motor. The 6.0L is a 364 cubic inch motor. That's 39 cubic inches more ! The 6.0L has the same stroke crank, but a much larger bore. It's going to be faster, but it will most likely get 1-2 MPG less.

I like fast, so there is no replacement for displacement for me. I could care less about that 1-2 MPG.

If you want just better mileage and a truck capable of 14.5 1/4 mile times, go with the 5.3L and you will save a few bucks. If you want to go even faster than that and still get better mileage than the 400, then your only choice is the 6.0L.

[bama51]

Hazieview, just curious what you decided on? I'm thinking about making this swap in the future and would appreciate your input since you've done the research.

[84 400]

Keep in mind the 99-03 5.3L and 4.6 can have piston slap problems. Ask me how I know......

A LSx, LS1, LT1 will get better millage then your SB400. There fuel inject. set up are far more efficent then the old carbs and TBI units. I would argue on the reliability aspect only because I have never had a carb motor let me down and leave me stuck not able to fix it and have had many issues with comp controlled motors.

The 5.3L's sure do run nice and drive smooth.

[OJOE]

my 85 short crew cab, 5.3 4l60e gets 16-17 mpg with plenty of power.