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Discussion Starter · #1 ·
Hello,
I just received a used Chevy 5.3L Vortec engine (LM7) out of a 2003 Silverado. Everything on it is stock at the moment and I would like to build it so that it can produce more than the stock 300 HP and keep it naturally aspirated if possible. I was already considering changing the cam, intake , and throttle body but would like to know what others have done with these engines and what's recommended. Thank you.
 

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2015 High Country Duramax
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I would set a realistic power goal, then build from there.

A reasonable cam, headers and good torque converter will get a nice little bump. Nothing crazy obviously though.

If you want to go more wild, you certainly can, but start to change the power curve that isn't ideal for truck use such as towing. But if your just looking for a nasty N/A build then you open the door to a really rowdy setup if you wanted.

The main thing is picking your parts carefully so they all work together, and not against each other.
 

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2003 Silverado 1500 LS
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I would look around the old Interweb for a tried-and-true 5.3L 'recipe', something that someone else has already assembled and dyno'd. Then I would focus mainly on down-low torque numbers. Even then, you're not gonna set the world on fire with a N/A 5.3L in a heavy pickup truck.
 

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Discussion Starter · #4 ·
I would set a realistic power goal, then build from there.

A reasonable cam, headers and good torque converter will get a nice little bump. Nothing crazy obviously though.

If you want to go more wild, you certainly can, but start to change the power curve that isn't ideal for truck use such as towing. But if your just looking for a nasty N/A build then you open the door to a really rowdy setup if you wanted.

The main thing is picking your parts carefully so they all work together, and not against each other.
Thank you for replying. I don't think I am looking for anything too wild and I am not sure what a realistic power goal is since this is my first LS engine. I was hoping to get maybe 50-75 more HP out of it, is that realistic? I definitely want to choose parts that work well together and that's the reason for my post, to seek advice from others that have done this successfully already. There are soo many different cam makes and models along with intakes and headers, I dont know which works well with each other. Thanks again.
 

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Discussion Starter · #5 ·
I would look around the old Interweb for a tried-and-true 5.3L 'recipe', something that someone else has already assembled and dyno'd. Then I would focus mainly on down-low torque numbers. Even then, you're not gonna set the world on fire with a N/A 5.3L in a heavy pickup truck.
This is mainly the reason for my post here. I was hoping someone would share what they did to their 5.3 that worked for them. Thanks.
 

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I have a great relationship with local machine shop, where the guys do mostly racing engines. I've had them work on a few of my own hot rod engines, really wonderful, honest, down-to-earth guys. They are just South of Boston, so if you're in that area, I can give you their name. If you know anyone like that, they would be the best people to ask, because they are building and dynoing these engines every day.

A big heavy truck needs LOTS of torquey power to make it really move out, and with a 5.3L, you might only attain those levels with boost. Not sure if it's worth it. If you build something that has HP only at high RPM's then you're gonna be disappointed, so be careful.
 

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1999 Silverado ECSB 6.0
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How about a 6.0 swap. A little bit more expensive then a cam swap but double the value.

If not that then just do a 212/218 high lift cam swap with some headers. Maybe a little intake and throttle body porting or jump up to the NNBS intake manifold and throttle body. Mill the heads a bit and you'll be good to go :)
 

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Discussion Starter · #8 ·
I have a great relationship with local machine shop, where the guys do mostly racing engines. I've had them work on a few of my own hot rod engines, really wonderful, honest, down-to-earth guys. They are just South of Boston, so if you're in that area, I can give you their name. If you know anyone like that, they would be the best people to ask, because they are building and dynoing these engines every day.

A big heavy truck needs LOTS of torquey power to make it really move out, and with a 5.3L, you might only attain those levels with boost. Not sure if it's worth it. If you build something that has HP only at high RPM's then you're gonna be disappointed, so be careful.
Thank you for the offer, but I am in GA. This engine was pulled from a 2003 Silverado, but I am building it to swap into my Jeep Wrangler.
 

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Check YouTube. I've been wanting to do the same for my silverado for a while and I've done a decent amount of research. I've seen a lot of good builds on there that give specifics on heads and cams other bolt on parts used and some even have dynos done showing results.

From what I gathered, you should be able to get up into the 400s with trick flow heads, cam, valve train, intake, intake manifold, headers, high flow cats, a good tune. Anything past that you're looking at turbo or charger builds.

I see you're swapping into a wrangler, that's going to be awesome. My neighbor had a 8" lifted TJ with an ls3 in it. T56 Trans, atlas transfer cases, bead lock wheels.....thing was awesome...youtube "ls3 jeep tj" you'll find it. It chirps 3rd gear and he dragged and beat a mustang from what I remember.

Either way good luck with your build...there should be other forums and sites/videos with build lists for 5.3l just might take a little digging...cheers.
 

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... This engine was pulled from a 2003 Silverado, but I am building it to swap into my Jeep Wrangler.
Ahh, cool. Then that engine may work out just great for you in a smaller Wrangler. I think one thing we ALL like on this forum here is pics and such, so if you get a chance, post up some engine and truck build pics after you get started on the project.

Good luck with it! 🇺🇸
 
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