454 vs. 5.3 efi vs. 5.3 carbed

[bloodybigblock]

As my headline states.... I have an 86 c20 crew cab that has a great stock 454 motor with TH400 trans. Im unsure of the actual mpg in the rig because i need a new carb. I was also going to buy an intake,headers,and run an exhaust. By the time i do that, ive spent $800-900 in parts. I was thinking about swapping in the 5.3 motor and still retaining my TH400 trans because its reliable,tough,and i can afford a sturdy 4l80E. Is it worth saving the $800-900 and selling my 454 to purchase the 5.3 Motor? My parts list came out roughly the same price of keeping the 454 with those bolt ons, having a efi 5.3 with camaro manifolds and tuned with motor mounts etc, or having a carbed 5.3 with the msd box and edelbrock intake..................... so which one would be best for daily driving? I thinking hp numbers will be in favor of ls motor while torque being held by the big block. Im also trying to figure out mpg increase. Is there a bonus to this swap......opinions?suggestions? Thanks guys for any comments

[68Stepbed]

I don't see any need for a 4L80E with the 5.3 unless you plan to make alot of power or do alot of heavy towing. Finding a good 5.3/4L60E combo and keeping it EFI would be uour best bet. With the proper tune,you would get more overall useable power and get better fuel mileage to boot.

I would only go carb on the LS if you just want to make more power with it with no concerns for fuel mileage.

You could sell the BB/TH400 as a combo and pick up a good complete 5.3/4L60E combo for around $1500 that would have all your wiring and ECM included.

[bk2life]

what are you asking?

what is better? they all have their own places in everyones heart.

personally a BBC is one of the best lookin motors you can put in a truck.

what are you really wanting? mpgs? grunt? torque? cool factor? cross country driving? tell us more.

[bloodybigblock]

Thanks 68step, I have easy access to a full combo, but i was thinking that a heavy crew cab would tire out the 4l60e. Ive not heard many good things about that trans.


BK2LIFE, i stated id like to drive it daily so of course mpg would be the main thing i was looking for. I mentioned horsepower and torque numbers because im sure itll effect the mpg along with trying to get that monster to start rolling lol. Can you or anyone else give me an idea on the mpg id gain on the ls conversion? Like i said, im unsure of the mpg im suppose to be getting with the big block. I know itll be alot of work,but maybe if i was getting 5mpg more it'd be worth it since i plan on driving daily (350miles a wk) Any helps or suggestions is appreciated.

[crossfire84]

cool factor = BBC
grunt = BBC
endless fun and waving as you drive past the gas pumps = 5.3 efi
just my 2 cents, and i have a BBC 396 in my 50

[bloodybigblock]

ill know more when i get an idea on mpg increase. i wont have any trouble selling the 454, just gotta get all the info and make a decision.

[BR3W CITY]

That 454 maybe makes 200hp/300lbft, assuming its in great shape, and will average maybe 9/12 mpg.

Stock 5.3 will be 285-305, average 15/19+mpg, if you choose to run an OD trans.

[hyatt]

If you do much towing You will be sick with a 5.3 after having a 454 Dont get me wrong The 5.3 is a great engine but for brute torque nothing beats a bigblock

[bloodybigblock]

Originally Posted by BR3W CITY

That 454 maybe makes 200hp/300lbft, assuming its in great shape, and will average maybe 9/12 mpg.

Stock 5.3 will be 285-305, average 15/19+mpg, if you choose to run an OD trans.

You think i can pull that off in my truck? It is a crew cab 3/4 ton. Ill usually cruise around 55mph on the highway since i live in the country. Also I will convert it to swb to make it attractive and save some weight. Im pretty sure my gears are 373 right now if that matters. Thanks man

[BR3W CITY]

Originally Posted by bloodybigblock

You think i can pull that off in my truck? It is a crew cab 3/4 ton. Ill usually cruise around 55mph on the highway since i live in the country. Also I will convert it to swb to make it attractive and save some weight. Im pretty sure my gears are 373 right now if that matters. Thanks man

I do 14/17 with a 6l and heavy/parasitic drivetrain and wheels. I'd think that with an o/d trans, reasonable wheel/tire combo, and a stock 5.3 there would be no reason you couldn't hit 19+, cruising. These are actually pretty efficient on the highway, locked up in top gear .

[bohmankid]

The 5.3 is more comparable to a sbc 350. It's a great reliable motor and will get good gas mileage and being efi it's a lot easier to tune IMO. Carbs are too sensitive for my liking.
The 454 will have more grunt. And also more of a cool factor. How about swapping in a vortec 454? That'd be sweet
They're both great. You just have to ask yourself if its worth the money to you.
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[yossarian19]

If you are dollars even on rehabbing the big block or going LS with EFI, I'd go LS with EFI. Wouldn't even consider going LS with a carb unless it would save you a bunch of money over keeping your BB and fixing it.
Sure a big block is cooler. Y'know what I think is even cooler than a big block, though? Saving an assload of money on gas & almost never having any reliability / tuning issues. 100K miles on a set of spark plugs. 10k factory spec'ed oil changes. Etc.
Now, if you don't want to drive a truck much & really want it to look sexy, speak "burnouts" fluently AND you have plenty of money to work with, go for a 409. All day every day - the W motors are sexier than anything running.
Big blocks and SBC come 2nd and 3rd in underhood appeal, if you ask me.
For real world miles / use, the LS with EFI is undisputed king.


ok, time for me to get off the soap box & go for a walk...

[mooseknuckles]

If you want an awesome daily driver go with the 5.3/4l60 and efi.

[bloodybigblock]

Thanks guys, its weird how you say "bbc is a cool factor" i think seeing an LS motor under a hood is cooler. Again, thanks for the info guys, i appreciate it.
BR3W CITY, i love your build man, thats a bada$$ ride you built man

[BossHogg69]

I think getting 19mpg in a 3/4 ton crew cab long bed will be extremely tough. Best I've ever gotten in my '05 GMC Sierra 1/2 ton 2wd ccsb is 18 on a straight highway drive going 60-65 mph, with a 5.3/4L60e and 3.73 gears. My truck weighs 5200# with me in it according to the scales at Reed Recyclers in Little Rock, AR. It usually gets mid 17's, but if I get on it very much that number goes down in a hurry.

FWIW, my '69 C10 swb would get 15mpg with a stockish 461 BBC (RV cam & 650 Holley) when I had it in front of my TKO500 5spd with a .68 5th gear. I tow with my GMC fairly often, and it does okay, but its definitely no big block.

As for the 'cool' factor, nothing about a stock plastic engine cover, ugly truck intake, or coil on plug valvecovers from a 5.3 look cool. With that being said, when they are detailed with some aftermarket parts, LS motors can look very nice - 68Stepbed's LS conversion is probably one of the best looking LS motors on this site. This post probably won't help you much, its just my .02

[bloodybigblock]

Originally Posted by BossHogg69

I think getting 19mpg in a 3/4 ton crew cab long bed will be extremely tough. Best I've ever gotten in my '05 GMC Sierra 1/2 ton 2wd ccsb is 18 on a straight highway drive going 60-65 mph, with a 5.3/4L60e and 3.73 gears. My truck weighs 5200# with me in it according to the scales at Reed Recyclers in Little Rock, AR. It usually gets mid 17's, but if I get on it very much that number goes down in a hurry.

FWIW, my '69 C10 swb would get 15mpg with a stockish 461 BBC (RV cam & 650 Holley) when I had it in front of my TKO500 5spd with a .68 5th gear. I tow with my GMC fairly often, and it does okay, but its definitely no big block.

As for the 'cool' factor, nothing about a stock plastic engine cover, ugly truck intake, or coil on plug valvecovers from a 5.3 look cool. With that being said, when they are detailed with some aftermarket parts, LS motors can look very nice - 68Stepbed's LS conversion is probably one of the best looking LS motors on this site. This post probably won't help you much, its just my .02

It helps, it kinda makes me ask more questions though. Im thinking my crew (when i make it shortbed) should weigh less than yours. Plus the few 100lbs from a iron BBC to an aluminum headed LS. Im sure it'd weigh under 5k. But your truck is a wee more aerodynamic then mine. Do you think with a tune, CAI,and better flowing exhaust could bring your mpg numbers up?

[BossHogg69]

Originally Posted by bloodybigblock

It helps, it kinda makes me ask more questions though. Im thinking my crew (when i make it shortbed) should weigh less than yours. Plus the few 100lbs from a iron BBC to an aluminum headed LS. Im sure it'd weigh under 5k. But your truck is a wee more aerodynamic then mine. Do you think with a tune, CAI,and better flowing exhaust could bring your mpg numbers up?

That was with a custom Blackbear 93 Octane tune (no handheld Hypertech junk), long tube headers, no catalytic converters, 2.5" dual exhaust and a K&N FIPK and iridium spark plugs... It went up 1mpg after all the mods. Then I added a Comp LSr 265 cam, and it went back to a little over 17 mpg highway, but I got greedy and added a Yank 2600 stall converter and bye bye fuel mileage (me sliding sideways from every stop light and doing rolling burnouts dont help either...)

I don't see how your truck will weigh much less even with the LS swap, but who knows, even if you do shorten the bed, it's still a 3/4 ton crew cab.

[prostreet1967]

Originally Posted by bloodybigblock

Thanks guys, its weird how you say "bbc is a cool factor" i think seeing an LS motor under a hood is cooler. Again, thanks for the info guys, i appreciate it.
BR3W CITY, i love your build man, thats a bada$$ ride you built man

Im n process of switching from BBC to 5.3 with turbo. I like how they look but loosing the weight and now the ease of power for low price was a no brainer for me.

[bloodybigblock]

I was thinking it'd weigh less. Ive read it weighs roughly 5250 as a long box and big block, either way, if i can cruise and get 17mpg then im saving money and having a reliable vehicle, cant go wrong with that. I plan on having roughly the same mods with it HP tuned. Thanks man

[BR3W CITY]

I kind of assumed that if you are converting it to SWB you were going to drop the 3/4 ton parts and go down to a 5lug 1/2t suspension. I guess you never said that specifically. BossHogg may be right that my estimate is a bit optimistic, seeing as my truck weighs about a half-ton less.

Curb on a 1/2 swb is 37-42 depending on equipment.

[Mr. 250r]

What about the best of both worlds... the 8.1! lol just kidding i would stay away from that motor but i do have to ask did the 1 tons have a 350 option because i've seen quite a few on CL that have a 350 that looks like its original and not swapped in although they could've done a really nice job.

Anyways like someone else said if your towing you might as well stick with the 454/400 especially with heavy towing maybe just swap in a 4l80 and gain OD but if you do go with a 4l60 please for the love of that tranny get a new sunshell i can't tell you how many of those come through my dads shop i would put money on it that they keep the transmission business alive lol, Im pretty sure GM ended up fixing the problem on their replacement shells but you could always be safe and buy the aftermarket ones

As far as looks go there is nothing original we haven't seen with the old school stuff especially car shows =-p if you want to spend the $$$$ on the LS it will look worlds better than any old setup does

[b454rat]

Put an OD tranny behind the 454. Also they make more power and torque than mentioned, little more horse but torque is close to 400.

Buddy had a Tahoe that was a 5.3, and I was not impressed. At all. I think my old 92 blazer with a 200k 350 had more power than that thing did....

Me, I'd stay with the 454. Build it up some, good heads, little more compression, little lumpy cam, carb/headers/intake/duals, etc. Put some 3.73 in it with an OD tranny, it will get better mileage and still be able to boil the tires off. These motors have been around since 1970 (454s, not big blocks) and still going. LS have been out for little over 10 years? Yes they are a good motor, but can't beat the power, sound and looks of a big block.

[68GMCCustom]

I'm confused as to why a 454 is being compared to a 5.3?

To be fair.....for 7.4liters of GenV BB V8...wouldn't a 4.8L LSx be a better comparison?









j/k...I mean a 6.0-6.2L of course!

[mooseknuckles]

Originally Posted by 68GMCCustom

I'm confused as to why a 454 is being compared to a 5.3?

To be fair.....for 7.4liters of GenV BB V8...wouldn't a 4.8L LSx be a better comparison?









j/k...I mean a 6.0-6.2L of course!

you may have just opened up a can of worms there.....lol

[bloodybigblock]

Originally Posted by 68GMCCustom

I'm confused as to why a 454 is being compared to a 5.3?

To be fair.....for 7.4liters of GenV BB V8...wouldn't a 4.8L LSx be a better comparison?









j/k...I mean a 6.0-6.2L of course!

Its funny because its true, Pretty sad