How much power can I make from a 5.3l LS with these limitations?

i have the lm7 in my 99 silverado and its plenty of motor in stock form. i had a 93 silverado with 350 before and its no comparison. my only add on is a flowmaster dual exaust system. sounds awesume but isnt obnoxious. i ave 18 mpg also. dont go newer than 09 on an LS or you will have to deal with afm.
 
Get ahold of Cam Motion.....They can custom grind a cam for your vehicle/engine combination.

In my opinion.....5.3L's are very limited unless you throw boost at them. Dyno numbers don't mean much for a mild street engine that'll spend most of it's life in lower & midrange parts of it's power band.

If you're going to go though the effort & expense of doing a swap......Use a better engine! A LY6 or a L96 Six Liter is a good start.
Or if you could find a LQ9/LQ4 Six Liter in decent shape.....These are getting up there in age & mileage.

And don't believe 5.3L's get better fuel economy than a 6.0L either....Especially in a heavy vehicle with the aerodynamics of a Barn. I swapped a LQ4 into my dads 2003 Tahoe to replace the leaky LM7 & even with the added load of higher Line Pressure in the built 4L65E....It gets the same if not a little better fuel mileage.
 
I’m only somewhat familiar with the GMT400 trucks which largely build on the square body C/K chassis. LS swap would be a lot of fun but also a lot of work - as you need to graft on things that truck didn’t have in 1987 - fuel injection(and maybe DBW), a “modern” 4-speed automatic with overdrive and CAN/GM LAN bus. A 5.3 ain’t gonna be much of an improvement over a carb’d 350. If I was going to do the swap all-out, the 6.0L and a built 4L-80E would be my pick. Else, the more sensible option would be a new 350 with Vortec heads(I think the Vortec heads should work with carbs and TBI) or a 383. It’s probably easier to get a EFI TBI/CSFI 350 from a newer GMT400 truck to work than an LSx.
 
I have never done an LS swap but I seriously doubt it is a drop in and plug and play operation. I can see fuel system, ECM, engine mount, cooling system, transmission fitment, and a host of other mods that may be needed just to make it work. I would do a lot of research first before I worried about how to make it produce more power.

I will be using a donor truck. It will take care of most of the conversion difficulties. Then I'll part out the rest of the truck and make most (if not all) of the money back that I spent buying the donor. So it's kind of like getting the engine and trans for free. It's a huge help.

sorry that's not going to work....cake and eat it too scenario right there...

I consider making that scenario work, one of my specialties in life. But I will say that most of this thread seems to have the wrong idea about what I'm trying to accomplish. They seem to think I'm trying to make a good deal more power than stock. I am not. If all you can gain is 16hp without harming MPG, that's fine by me. I just wanted to go ahead and get that 16 hp. Although from my research, the situation does seem a little better than that.

I don't want to be rude but you're talking in circles. Engines are nothing but air pumps and the more air you pump the more power you get. If you don't want to improve air flow with porting and polishing the heads or changing the lift and duration of the camshaft AND putting a high flow header system and extractor on the engine and you don't want to increase fuel flow which would definitely be dictated by the greater air flow then what specifically do you want to change? There is no free lunch.

Well I don't want to be rude either, but several posts in this thread prove you wrong. A simple full exhaust upgrade nullifies your post. And the free lunch is a bad example, there won't be anything free about these upgrades. They will cost plenty.

Get ahold of Cam Motion.....They can custom grind a cam for your vehicle/engine combination.

In my opinion.....5.3L's are very limited unless you throw boost at them. Dyno numbers don't mean much for a mild street engine that'll spend most of it's life in lower & midrange parts of it's power band.

If you're going to go though the effort & expense of doing a swap......Use a better engine! A LY6 or a L96 Six Liter is a good start.
Or if you could find a LQ9/LQ4 Six Liter in decent shape.....These are getting up there in age & mileage.

And don't believe 5.3L's get better fuel economy than a 6.0L either....Especially in a heavy vehicle with the aerodynamics of a Barn. I swapped a LQ4 into my dads 2003 Tahoe to replace the leaky LM7 & even with the added load of higher Line Pressure in the built 4L65E....It gets the same if not a little better fuel mileage.

Interesting post. If I take your meaning, you're saying go with a 6.0L instead because they're better suited to my needs than the 5.3L. Because you get a power increase without a noteworthy decrease in fuel mileage. In fact MPG may increase a little.
 
In 1987 that motor was likely choked up with intake and especially exhaust restrictions. So I could see a bump in both power and mpg with the motor uncorked and able to breath--yes, put your foot into it and it will hurn gas, but keep your foot out and it should breath easier and make more mpg.

Rebuilding a 350 vs LS swap, not sure what is easier. Or cheaper. The old mill is going to benefit from newer heads while the LS won’t need touching. TBI works but is hardly worth using, so that is more money to upgrade/replace. If you have a donor truck then it may be easiest to swap.
 
Interesting post. If I take your meaning, you're saying go with a 6.0L instead because they're better suited to my needs than the 5.3L. Because you get a power increase without a noteworthy decrease in fuel mileage. In fact MPG may increase a little.

That is what I mean, Even a lowly 300hp LQ4 6.0L is an upgrade over a 310hp L33 5.3L because the 6.0L will make more power & torque under the curve which is more efficient at moving heavier vehicles.

Stay away from '99 & '00 LQ4's because their Iron Heads & extended Crankshafts.
 
i have the lm7 in my 99 silverado and its plenty of motor in stock form. i had a 93 silverado with 350 before and its no comparison. my only add on is a flowmaster dual exaust system. sounds awesume but isnt obnoxious. i ave 18 mpg also. dont go newer than 09 on an LS or you will have to deal with afm.
I haven't driven a TBI 350, but I had a '96 C1500 with a 350 (Vortec) and I loved that motor.

I've driven an '03 Silverado 5.3L and '05 Tahoe 5.3L and they were gutless. My 350 would have flown past them.
 
Holley swap parts are expensive but fit better than anything I've ever used.

I would recommend against a 4L80E, A well built 4L60E/4L65E is MUCH more efficient.
 
my99 5.3 has mechanical throttle body. much more responsive than the drive by wire later ones. its much faster than any 350 tbi or carb i have driven . the 350 is a dinosaur compared to the LS engine. that is till GM went to AFM! ruined a masterpeice
 
I haven't driven a TBI 350, but I had a '96 C1500 with a 350 (Vortec) and I loved that motor.

I've driven an '03 Silverado 5.3L and '05 Tahoe 5.3L and they were gutless. My 350 would have flown past them.

5.3 is something like 110 more hp than the 350. And 30 more tq, if both are stock. It's probably not a good comparison if the 5.3L is in a 6k lb tahoe. Was your truck a single cab? If so it as a lot lighter than either of those vehicles that had the 5.3L. I notice you did say a 96 model. They did get a bump in power, but my old 87 ain't included in that. It's something like 180hp when it was new. That's before 200k miles were put on it. Just switching to a stock 5.3L will make it feel like a very different and much faster vehicle.

Holley swap parts are expensive but fit better than anything I've ever used.

I would recommend against a 4L80E, A well built 4L60E/4L65E is MUCH more efficient.

I've heard to stay away from the 60e, everyone says they are too weak. But a built one is of course a different story... could you elaborate a bit on why it would be more efficient than a 4L80e?
 
I will be using a donor truck. It will take care of most of the conversion difficulties. Then I'll part out the rest of the truck and make most (if not all) of the money back that I spent buying the donor. So it's kind of like getting the engine and trans for free. It's a huge help.



I consider making that scenario work, one of my specialties in life. But I will say that most of this thread seems to have the wrong idea about what I'm trying to accomplish. They seem to think I'm trying to make a good deal more power than stock. I am not. If all you can gain is 16hp without harming MPG, that's fine by me. I just wanted to go ahead and get that 16 hp. Although from my research, the situation does seem a little better than that.



Well I don't want to be rude either, but several posts in this thread prove you wrong. A simple full exhaust upgrade nullifies your post. And the free lunch is a bad example, there won't be anything free about these upgrades. They will cost plenty.



Interesting post. If I take your meaning, you're saying go with a 6.0L instead because they're better suited to my needs than the 5.3L. Because you get a power increase without a noteworthy decrease in fuel mileage. In fact MPG may increase a little.
I like your plan about getting a donor vehicle, but take advantage of the donor vehicle to the max. Also bring along the 6-speed automatic, because that alone will contribute to better fuel economy. A late-model 6.2 L86 and 6-speed auto transplanted as a unit with the control boxes and wiring harnesses would save a lot of electronic figuring-it-out problems. And a stock 6.2 L86 makes 420 HP while getting better fuel economy than the old 350. And the 5.3L L83 makes 355 HP, which is 145 more than what a 1987-vintage 350 makes. It will make your truck better in every way: performance, fuel economy, and smoothness.

No need to do anything to the engine because it already makes more power than you ever dreamed of out of the 350. But if you feel you must, check out any number of Richard Holdener videos on YouTube to see how the new engines respond to bolt-on components. Or just go to Brian Tooley Racing and buy their Truck Norris cam.
 
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by all means use a 4l80 over the 460. most of my friends have burned their 4l60e trans up . unless you get one built with heavy duty parts the 4l60 is too weak for the LS in the long run
 
5.3 is something like 110 more hp than the 350. And 30 more tq, if both are stock. It's probably not a good comparison if the 5.3L is in a 6k lb tahoe. Was your truck a single cab? If so it as a lot lighter than either of those vehicles that had the 5.3L. I notice you did say a 96 model. They did get a bump in power, but my old 87 ain't included in that. It's something like 180hp when it was new. That's before 200k miles were put on it. Just switching to a stock 5.3L will make it feel like a very different and much faster vehicle.
The 5.7L Vortec had 255hp while the 5.3L in 2003 had 285hp. Plus a real throttle cable and not drive-by-wire was very responsive, could melt the rear tires. That 5.3L had as much of a chance to burn rubber as my 2.2L Camry. (Hint: 0% chance).
 
I've heard to stay away from the 60e, everyone says they are too weak. But a built one is of course a different story... could you elaborate a bit on why it would be more efficient than a 4L80e?

That's the problem with LS engine enthusiast forums, Same crap get's regurgitated over & over again. There are millions of 4L60E/4L65E units that lived LONG lives.
There is no questioning that a 4L80E will handle more power/torque/weight/abuse than a 4L60E, But if you don't make 450+ pounds of torque.....You DO NOT need a 4L80E!

Everything in a 4L80E that rotates is made of cast iron or steel & are 2-3 times heavier than the rotating components in a 4L60E.

I've had both a 4L60E & a 4L80E in my Camaro, The difference was shocking even to me that's done a ton of swaps. With the 80E.....It's like I was dragging a Anchor around unless I was at full throttle. Even then the effect was there judging from my 60 foot times. My mileage also took a 3MPG hit.

The 6L80E/6L90E is a great choice & very efficient, Once you install a TransGo programming kit, Billet Front Twin Disc Converter, And some Tuning.....They're Bad**s!!

However.....To install one & have the driveline angles correct.....The Trans Tunnel will need modifications!
 
The 5.7L Vortec had 255hp while the 5.3L in 2003 had 285hp. Plus a real throttle cable and not drive-by-wire was very responsive, could melt the rear tires. That 5.3L had as much of a chance to burn rubber as my 2.2L Camry. (Hint: 0% chance).
Idk, our 2004 Silverado would annihilate a tire (woo open diff!) no problem. But GM’s drive by wire programming left something (a lot) to be desired…

You can make a drive by wire system just as responsive as a mechanical throttle, or even more or less depending on what you want. Just need to adjust it with a tuner. Heck, people are out there spending $300 on “pedal commanders” to do exactly that because they’re afraid to hit the pedal harder 🤣
 
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