Some 5.3L questions

[bennylava]

Here are my 5.3L questions that I'm hoping someone who knows that engine very well can answer.

1. How much power can you make without affecting MPG (much)?

2. Any estimate on what kind of fuel mileage you'd get with 550hp?

3. What kind of longevity can be expected out if those are your power numbers? Will that engine make it past 100k miles if properly maintained? 200k miles?

4. Are the factory heads any good for making power?

5. Is it easy (enough) to get to 500+ hp while still being naturally aspirated? Or is this where everyone adds a turbo? I want to stay NA.

6. Is it difficult to find a Gen3 junkyard 5.3L?

7. Is the best test of a Junkyard 5.3L to pop the valve covers and look for sludge?

8. What kind of power can you make staying naturally aspirated, and keeping the stock heads? With better headers, upgraded roller rockers, good exhaust system, etc. How much can you squeeze out of it?

Thank you!

[cdub2010]

ok, ill give my two cents but ill need them back cause i gotta buy gas.

1- I say stock its 300hp
2- single digits, gonna need a lot of fuel to get 550 hp.
3- my supercharged 5.3 made 400hp lasted 170k until the truck got wrecked.
4- id say yes
5- how deep is your pockets 550hp is a big ask on na
6- lots of 5.3's on marketplace for $450- to $1200 around me
7- clean heads and covers are nice, dont buy a rusted hunk of junk.
8- Id doubt you could get 350hp out of those upgrades.

Best hp per dollar for a 5.3's is to add a turbo. why reinvent the wheel turn up the boost to your wanted power level, blow up and repeat.

https://sites.google.com/site/sloppy...unkyardturbols

[bennylava]

Well I want to play the efficiency game. I want to stay near stock fuel mileage. I have heard that turbos actually make the engine more efficient, not less. Hopefully that's true.

[cdub2010]

The supercharged 5.3 was a real mild tune in a 2004 yukon xl. It made the truck fun to drive but it was nowhere near a fast truck. With the awd and boost It would spook people off the line but it really didnt have much after that. The mileage of under 15 and need for premium fuel really sucked the fun out of it being a daily driver and all.

Compare it to my 08 yukon. supposed built NA 6 litre, 4l80e with mild cam setup for boost. Its pretty similar quickness but its mileage was about 12 mpg. I have a 78/75 turbo for it but everything is on hold now. I really cant believe the mpg would get better. but you never know.

[bennylava]

Well it doesn't have to get better, but I can at least make sure it doesn't get any worse. At these fuel prices 14-19 mpg is low enough.

[toolboxchev]

Here is a thought to be divisive.

If I am going to pay the Biden Admin to go fast, drive a big brick, and generally haul ass, I am looking a 6.0 or 6.2.

Mild upgrades, better 6 speed trans and possibly a turbo would put me there in the 550 range.

That would move on the street, but not beat any Porsche.

Then again I might have to outdo Farm Truck and be famous!

[Accelo]

With a Turbo mileage goes down.
It doesn't have to but it takes fuel to accelerate and if you want to go faster it takes more.
My point is why put a turbo on it if you don't use it?
So, ya it will use more fuel.

[red71cheyenne]

Are the 5.3's any harder to rebuild vs the older 350's?

The wifes sub is approaching 200K and I figure it will be time before long.

[Accelo]

The LS motors last longer than any typical 350, especially the ones with a carburetor.
A lot of reasons for this;
Better oils
Low tension rings
Roller camshafts
Better control of the air fuel mixtures
Better ignition controls/wiring
Improvements in metallurgy.

Of these the "better control of the air fuel mixtures" is likely the most important.
No more washing cylinders with fuel and dilution of the oil with fuel.
This caused a lot of wear, on the first gen motors, especially upon startup.
It was common to see cylinder wear in the .007 to .0011 @ 100,000 miles on SBC's.
Many LS motors still have the cylinder hatch marks showing at this benchmark.

These are the same reasons the oil change interval has been extended from 3000 to 5000 miles.

With reasonable care I would expect 300k miles on a modern LS motor.
No the 5.3 are not more difficult to rebuild than the first gen 350 motor.
Replacing the head bolts, torque to yield bolts, adds to the cost but isn't more complicated.
The fact they last so much longer between rebuilds reduces the cost per mile.
Cheers.