Are 4.8l vortecs really worth it?

[rs74]

I am considering not putting the new 355 down in the short bed for this build. My ultimate goal was to find an LS1 or 2 engine or something of the like to put in. The vortecs seem to be a cheaper find. I am trying to keep mpg's in mind but at the same time want some pep. I see alot of guys doing the 5.3's and 6.0's but never hear about the 4.8. I do like to run hard at times.

The 355 will fulfill my needs for power but mileage is going to suffer a bunch. IF I can have the best of both worlds what should I consider. I have a 6.0l in my 03 2500hd and like it. Realisticlally will any of these engines get close to 20 mpg with say a 4l60e trans. I think my gears are 3.73's.
This started with the 4.8l and since it is the smallest I thought maybe it might get the best mileage.

[68Timber]

I've wondered the same thing. They come rated around 20 hp less than the 5.3, but what happens when you turn the wick up?

[rs74]

I would imagine you are going to have to get a tune anyways so that should ad a bit to the 4.8. I would most certainly be happy with an ls but they are usually alot more money.

[comegetsome2003]

Ive had a couple of 4.8 trucks and several 5.3 trucks.....there is very little difference power wise in stock form....local guy has a 03 silverado that had a cammed 4.8 in it.....spun a bearing he bought a junkyard 5.3 put same cam in it with exact same boltons and it run within 1 tenth
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[rs74]

Originally Posted by comegetsome2003

Ive had a couple of 4.8 trucks and several 5.3 trucks.....there is very little difference power wise in stock form....local guy has a 03 silverado that had a cammed 4.8 in it.....spun a bearing he bought a junkyard 5.3 put same cam in it with exact same boltons and it run within 1 tenth
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Then why do so many go with the 5.3l's? Is it the bigger is better syndrome. I get why they choose the 6.0l but it the 5.3 and 4.8 are all but identical then I don't get it.

[comegetsome2003]

Just alittle more power i guess....if i was goin to a junkyard and could get a 4.8 and 5.3 for same price id take the 5.3....exact same as i would take a 350 over a 305....if you can stumble across a 6.0 id jump on it....ive seen a few pop up around my region between 700-1000
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[Ziegelsteinfaust]

I had the new 07 GMC rcsb with the 4.8. With the basic bolt-ons, TB torque converter, 4.56 gears, tune, 255/60/17 tires, and it would routinely get 21mpg hwy.

A guy who lived in the Town house complex next to mine dropped a 4.8 in his 75 rcsb, and with stock 3.42 gears. At the point I knew him just before I had to move. He was on the down hill slide to getting his truck 100%, and at that point his best mpg during a freeway shake down was almost 25mpg. Would spank my truck 0-60, mpg, and about everything else that mattered. He had the bolt-ons to get it in his truck, and no tune except to get the codes turned off.

So I don't see why you couldn't do the same, as these old trucks are so much lighter then the new ones. Often by almost 1000 pounds.

[68Timber]

Originally Posted by Ziegelsteinfaust

I had the new 07 GMC rcsb with the 4.8. With the basic bolt-ons, TB torque converter, 4.56 gears, tune, 255/60/17 tires, and it would routinely get 21mpg hwy.

A guy who lived in the Town house complex next to mine dropped a 4.8 in his 75 rcsb, and with stock 3.42 gears. At the point I knew him just before I had to move. He was on the down hill slide to getting his truck 100%, and at that point his best mpg during a freeway shake down was almost 25mpg. Would spank my truck 0-60, mpg, and about everything else that mattered. He had the bolt-ons to get it in his truck, and no tune except to get the codes turned off.

So I don't see why you couldn't do the same, as these old trucks are so much lighter then the new ones. Often by almost 1000 pounds.

Good info there.

[rs74]

I didn't realize that the new trucks were that much heavier. I would have thought with most of them plastic anymore they would be comparable. Thanks.

[Ziegelsteinfaust]

Originally Posted by rs74

I didn't realize that the new trucks were that much heavier. I would have thought with most of them plastic anymore they would be comparable. Thanks.

The new trucks frames are stronger, and boxed vs our old C channel style. Plus all the saftey equipment, sound deadening, and the new seats weigh more then the old style bench. Out A-arms weigh about 13 pounds, and the newer cast versions seem to me to weigh 20.

It all adds up, and eventually it exceeds all common sensibility.

I imagine if I was serious about putting my fat girl on a serious diet, keeping comfort in mind, and handling as a goal. I could easily dip below 3500 pounds, or 200 pounds below a rcsb.

Mind you it would require a modern engine, light weight bucket seats, conversion to a rcsb using a later bed, and fiberglass front end. Depending on how crazy your willing to get you could easily beat my estimates by quite alot.

Although I don't think hwy mpg would go up, because weight would not be a factor anymore. City mpg would from less weight to accelerate. Then handling would improve from lack of weight.

[gchemist]

I would put a 4.3 or 5.3 in my 96 Jimmy in a hearbeat!!

[Tx Firefighter]

I remember some years back one of the magazines did an article to get stupid power out of a 5.3. They kept turning it up to crazy horsepower levels until they finally popped the engine. The funny part of the article was when they tore the engine down to dissect the damage, they found that the engine was actually a 4.8 all along and not the 5.3 that they thought it was.
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[INSIDIOUS '86]

Originally Posted by Tx Firefighter

I remember some years back one of the magazines did an article to get stupid power out of a 5.3. They kept turning it up to crazy horsepower levels until they finally popped the engine. The funny part of the article was when they tore the engine down to dissect the damage, they found that the engine was actually a 4.8 all along and not the 5.3 that they thought it was.
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They turbo'd it on car craft and eventually made 1200hp lol
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[tinydb84]

Originally Posted by INSIDIOUS '86

They turbo'd it on car craft and eventually made 1200hp lol
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Im pretty sure the article was titled big bang theory or something similiar

[y5mgisi]

It was the big bang theory. 1200hp on a stock, junkyard 4.8 bottom end. Had aftermarket heads, cam, and a bunch of boost.

[INSIDIOUS '86]

History has dictated that for mpg a smaller engine was always a better start. If you want mpg go with a 283 or 305 both will have less apatite for fuel my freinds 78 Camaro with a 283 with an edelbrock with a th350 and 2:73 gears pulled 32mpg on the highway and 19city. How do we know for sure? We used a clear gas can with precision measuring for the tests.
A 305 was built to use less gas than most v8s but still do the same amount of work.

If you go with a new ls motor then would suggest keeping the active fuel manegment stuff along with it

As for me a 283 with a tpi setup and tbi heads and tri y headers is going to do just fine as my daily driver combined with a 700r4 and 3:08-3:42 gearing I'm confident in 30mpg on the highway
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[68Timber]

Originally Posted by INSIDIOUS '86

As for me a 283 with a tpi setup and tbi heads and tri y headers is going to do just fine as my daily driver combined with a 700r4 and 3:08-3:42 gearing I'm confident in 30mpg on the highway
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Looking forward to this. Smaller V8's that run like a sewing machine are cool. The tuned port injection should feed it well considering it was designed for the 305. Will your 283 rev higher before it noses over? Seems like a smaller cube motor wouldn't run out of adequate intake as quickly but the difference may be too small to matter. If not, it's still a great looking system that'll help the 283 make all the tq it can. Cool build.

[INSIDIOUS '86]

Originally Posted by BRUISER

Looking forward to this. Smaller V8's that run like a sewing machine are cool. The tuned port injection should feed it well considering it was designed for the 305. Will your 283 rev higher before it noses over? Seems like a smaller cube motor wouldn't run out of adequate intake as quickly but the difference may be too small to matter. If not, it's still a great looking system that'll help the 283 make all the tq it can. Cool build.

Both the too and tbi heads kill top end. Plus I don't think the cam will pull over both those limits. But we will see. Should still have decent power compared to anything else on the road and highway.
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[Oilbrnr]

I'm putting a late '07 4.8 in my K5. I'll let you know in a few months!

If only maggies weren't so expensive!

[68Timber]

Originally Posted by Oilbrnr

I'm putting a late '07 4.8 in my K5. I'll let you know in a few months!

If only maggies weren't so expensive!

Cool! Non-AFM motor, eh? Same tranny?

[Oilbrnr]

Originally Posted by BRUISER

Cool! Non-AFM motor, eh? Same tranny?

For now, the same original SM465/NP205 combo. That being said, I'm on the active lookout for the elusive round 205 or an '89 241 to put behind a NV4500 a la DirtyLarry. Also looking for some sage cam advice. Should I just leave what it has, or is there something that might give her a slight bump with the right tune...

The K5 is my DD just to save wear and tear on my Dmax, esp since I drive 6 miles of washboard dirt road every day. Objective is to have equal or more power then the original 350 and pick up a few MPG plus all the other small benefits that come with a modern engine.

[68Timber]

What happened to the 241 in '89? I have one in my 85 and have an auto to manual swap planned.

[Oilbrnr]

Originally Posted by BRUISER

What happened to the 241 in '89? I have one in my 85 and have an auto to manual swap planned.

I believe it to be the only year with a cable driven speedo which is what I want to stick with given the fact that my '77 has a nice original tach cluster. 90-1 had VSS (great for a LS conversion though). Unsure about '88 at this point.

I still need to do more research, but the LS swap is the first priority at this point.

[ivorton74]

today I took a small trip on my job in a 2012 chevy 3500 van. I was amazed at how much power and get up and go it has for such a big van. now im thinking I might want a 6.0. how much difference is the mileage in the 6.0 than a 4.8 or 5.3? cuz after that I started thinkin to myself man only if my truck had this much power.

[rs74]

Originally Posted by ivorton74

today I took a small trip on my job in a 2012 chevy 3500 van. I was amazed at how much power and get up and go it has for such a big van. now im thinking I might want a 6.0. how much difference is the mileage in the 6.0 than a 4.8 or 5.3? cuz after that I started thinkin to myself man only if my truck had this much power.

Wouldn't that just tear you up? Getting beat buy a van.