5.3 vs 5.7
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From: over dere
in stock form, apples for apples, there's more like a 40 hp difference between the two. the earlier non HO 5.3 came with basically the same heads as an ls1, and was around 310 hp. ls1's were 345-350 hp.
later 5.3's got LS6 style heads and were bumped to 325 hp.
it's not a matter the percentage of displacement loss. the 5.3 is basically an underbored ls1. smaller bores change the flow characteristics of the heads.
so how much less will a 5.3 make than an ls1? some. but if you get an iron block 5.3 you can bore them out to ls1 specs.
later 5.3's got LS6 style heads and were bumped to 325 hp.
it's not a matter the percentage of displacement loss. the 5.3 is basically an underbored ls1. smaller bores change the flow characteristics of the heads.
so how much less will a 5.3 make than an ls1? some. but if you get an iron block 5.3 you can bore them out to ls1 specs.
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From: over dere
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From: Dirty South
And what LS1 are you quoting that made 345-350 hp . I do hope your not trying to use some old exaggerated factory gross rating. In order to compare this you need see what theses two put down to the ground , not some inflated factory gross rating. I will say it again there is not 40 hp difference between the two.
And what LS1 are you quoting that made 345-350 hp . I do hope your not trying to use some old exaggerated factory gross rating. In order to compare this you need see what theses two put down to the ground , not some inflated factory gross rating. I will say it again there is not 40 hp difference between the two.
5.3s were rated at 270hp-295hp depending on year, the HO 5.3 at 310hp due to higher compression flat top pistons and 799 heads
A fairly good indicator is that the ls1 in an automatic trans car will make 290-310rwhp while a 5.3 truck will make low-mid 200s (mine made 220rwhp with dual exhaust and a mild tune). It's common for cammed and longtube 5.3s to be in the same rwhp range as a stock ls1 car. (some of that will be due to higher drivetrain loss).
If I remember correctly a few years ago someone took a 5.3 and swapped on: ls6 intake, 243 heads, ls6 cam, and longtubes. It made around 350rwhp in a swapped car.
A 5.7 ls6 car with longtubes will make a solid 20-30rwhp more than that.
That's the closest comparison I can think of.
A 5.7 ls6 car with longtubes will make a solid 20-30rwhp more than that.
That's the closest comparison I can think of.
On The Tree
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From: Dirty South
LS1s were under rated at 305-320 hp in many forms...but the truth is all LS1s make ~345hp crank they just wanted the corvette to look better on paper
5.3s were rated at 270hp-295hp depending on year, the HO 5.3 at 310hp due to higher compression flat top pistons and 799 heads
A fairly good indicator is that the ls1 in an automatic trans car will make 290-310rwhp while a 5.3 truck will make low-mid 200s (mine made 220rwhp with dual exhaust and a mild tune). It's common for cammed and longtube 5.3s to be in the same rwhp range as a stock ls1 car. (some of that will be due to higher drivetrain loss).
5.3s were rated at 270hp-295hp depending on year, the HO 5.3 at 310hp due to higher compression flat top pistons and 799 heads
A fairly good indicator is that the ls1 in an automatic trans car will make 290-310rwhp while a 5.3 truck will make low-mid 200s (mine made 220rwhp with dual exhaust and a mild tune). It's common for cammed and longtube 5.3s to be in the same rwhp range as a stock ls1 car. (some of that will be due to higher drivetrain loss).
The ls6 equipped 5.3 versus a true ls6 was the closest comparison I could think of since both use GM parts rather than trying to find similar builds using the same aftermarket cam/heads/intakes.
If you search truck forums you might be able to find some accounts of people boring a 5.3 to accept ls1 pistons and get a better feel for how they stack up. Before and after, but more likely the person also upgrades cams when they get more displacement.
HP will end up being relatively close IMO, but the 5.3 will be down on torque.
On The Tree
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From: Dirty South
I agree, just not a perfect comparison available. I took the OP's post more as a comparison of factory available engines.
The ls6 equipped 5.3 versus a true ls6 was the closest comparison I could think of since both use GM parts rather than trying to find similar builds using the same aftermarket cam/heads/intakes.
If you search truck forums you might be able to find some accounts of people boring a 5.3 to accept ls1 pistons and get a better feel for how they stack up. Before and after, but more likely the person also upgrades cams when they get more displacement.
HP will end up being relatively close IMO, but the 5.3 will be down on torque.
The ls6 equipped 5.3 versus a true ls6 was the closest comparison I could think of since both use GM parts rather than trying to find similar builds using the same aftermarket cam/heads/intakes.
If you search truck forums you might be able to find some accounts of people boring a 5.3 to accept ls1 pistons and get a better feel for how they stack up. Before and after, but more likely the person also upgrades cams when they get more displacement.
HP will end up being relatively close IMO, but the 5.3 will be down on torque.
Also add the fact that even with the exact same cam in the 5.3 and 5.7 , the 5.7 will run smoother, so you can go with a bigger cam. Furthermore. all else being with the engines equal cubic inches rule, if you're strictly running a naturally aspirated engine an want to make maximum hp/tq.
Last edited by 99Bluz28; Dec 19, 2014 at 04:52 PM.
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