5.3 compared to 5.7

[RED TAHOE LS]

Just curious how you think the two engines compare. My Tahoe 5.7 Vortec is as strong as it was when new. I've played with few 5.3's while entering freeway and notice one close to my rear bumper, so I just ease into it and have yet found one that compares to the torque. Just curious.
David g...........

 

[iamdub]

More power per cube, lighter, smoother, less potential for leaks, more efficient, stronger architecture. The Gen3 5.3 has 30-55 more HP but about 20 lb-ft less TQ. I'm sure the loss in TQ is from the smaller displacement and cam chosen to help with fuel economy which resulted in higher HP.

Punch the 5.3 out to a 5.7 and run the same sized cam as the Gen2 5.7 and the Gen3 would beat it in numbers as well as all the other attributes.

 

[swathdiver]

Just curious how you think the two engines compare.

Help revive my memory David, what's the horsepower and torque ratings of the motor and how much does your truck weigh?

My LC9 is rated at 310 HP @ 5200 RPMs and 335 FT/LBS Torque @ 4400 RPMs. It's detuned some compared with Chris' Tahoe for example which if memory serves makes 320 @ 5200 and 340 Torque @ 4200 that year. When the 5.3s got VVT the peak torque came in at 4000 RPMs and 5 FT/LBS less and HP peaked at 5400 RPMs. Them new Gen V L83s make over 350 horses.

 

[RED TAHOE LS]

James, thanks for the reply, never having put my Tahoe on scales, I'm thinking probably in the 5000 # range. I'm not a numbers guy, just recognize power easily, and since it has 3.73 gears, the 255 hp makes for a lot of zip with a good trans.
Rated hp was flopped around by mfg's like a yo yo in the late 60's/70's to help sell muscle car's so that the average guy could get affordable insurance. Since being a gm guy for a long time, everyone remembers the Z/28 camaro's from 67-69, they were rated @ 290 hp which was a joke.
Having campaigned a 1970 SS/DA Hemi Cuda in NHRA Division 2 , I know what performance feels like.
I was just getting pros/cons of the comparison.
David g.........

 

[swathdiver]

My calculated RWHP through the traps is 302 horsepower. That's with one bad cat and a BlackBear tune. Your SBC of course generally makes way more torque than horsepower and were low-revving engines compared with the LS. Actually, I don't know what engine you have, what is it?

 

[iamdub]

My calculated RWHP through the traps is 302 horsepower. That's with one bad cat and a BlackBear tune. Your SBC of course generally makes way more torque than horsepower and were low-revving engines compared with the LS. Actually, I don't know what engine you have, what is it?

Likely the L31.

 

[RED TAHOE LS]

Just thought it was a simple question, rest my case.

 

[swathdiver]

I looked up your L31, thanks Chris, and that is a great engine. Nice flat torque curve and you and I know torque is what get them moving and the more down low the better.

 

[rockola1971]

I own (2) 5.3L (In 03 Tahoes) (Not including the one sitting on my engine stand and one sitting on a pallet) and I own a 5.7L equipped Z71 Sierra (Vin R) and I can tell you hands down the 5.7L equipped Sierra pulls my 5400lb 32ft camper better. My 5.3L Tahoes do ok but the 5.7L just has the torque and in the right place to get the weight moving.

 

[swathdiver]

...the 5.7L just has the torque and in the right place to get the weight moving.

Down low! This is why GM went with the 6-speeds to get the 5.3 trucks moving; first gear final drive is 13.77:1!

 

[iamdub]

Down low! This is why GM went with the 6-speeds to get the 5.3 trucks moving; first gear final drive is 13.77:1!

Which makes me wonder why the earlier GMT800 trucks commonly had the 3.08 rear gears. When cruising at 50ish, it was like the engine was barely above idle. Great for fuel economy, but poor for getting things moving, towing or not.

My '08 has 3.73 and it's a dog off the line compared to mid- and upper-RPM.

No doubt the L31 was/is a great motor. It's just not as efficient as it's replacement in terms of power per cubic inch and the fuel used to make that power. I guess the closest comparison displacement-wise would be the LS1, although it is actually negligibly smaller at 5,665cc to the L31's 5,736cc, a .071 liter difference. With the power numbers, the LS1 wins hands-down with 90 HP and 20 lb-ft over the L31. The huge difference is that the L31 makes it's peak TQ at 2,800 RPM whereas the LS1 makes it's at 4,400 RPM.

When comparing truck motor to truck motor, that would be the LM7, the L31's replacement. Again, the LS-series wins in efficiency and HP numbers. Yet again, this is at higher RPM which is a bit counter-productive in a truck application. Gearing is the saving grace here.

 

[swathdiver]

Government regulations such as CAFE Standards force the manufacturers to favor fuel economy over common sense.

Is it still doggy off the line after the tune? Mine's going to get me in trouble with the law sooner or later! I made a turn yesterday and nailed it and spun sideways even with traction control flashing on the dash, flash backed to my Buick days!

 

[iamdub]

Government regulations such as CAFE Standards force the manufacturers to favor fuel economy over common sense.

Is it still doggy off the line after the tune? Mine's going to get me in trouble with the law sooner or later! I made a turn yesterday and nailed it and spun sideways even with traction control flashing on the dash, flash backed to my Buick days!

I'm quite sure tightened gubbamint standards are what dictates such things. I'm just glad we can still modify our vehicles after the fact.

It may be stronger off the line, but not by much. I don't punch it because of the broken mount. Even easing into it to get started then quickly going WOT, it still pulls notably harder from around 3,000 and up. It really is like VTEC engaging. It's not such a gradual increase. Once I get that mount replaced (won't happen until I get long tubes), I'll be able to get consistent results. This all may be perfectly normal and the nature of the beast- I have nothing to compare it to. My S10 was the opposite where it pulled hardest from around 1,500-3,500 then quickly fell off from 4,000 up. It had a 4.3 that is essentially 3/4 of the 5.7 in David's Tahoe so it stands to reason that it'd have similar characteristics.

 

[rockola1971]

I'm quite sure tightened gubbamint standards are what dictates such things. I'm just glad we can still modify our vehicles after the fact.

It may be stronger off the line, but not by much. I don't punch it because of the broken mount. Even easing into it to get started then quickly going WOT, it still pulls notably harder from around 3,000 and up. It really is like VTEC engaging. It's not such a gradual increase. Once I get that mount replaced (won't happen until I get long tubes), I'll be able to get consistent results. This all may be perfectly normal and the nature of the beast- I have nothing to compare it to. My S10 was the opposite where it pulled hardest from around 1,500-3,500 then quickly fell off from 4,000 up. It had a 4.3 that is essentially 3/4 of the 5.7 in David's Tahoe so it stands to reason that it'd have similar characteristics.

Im digging the color of your ride.

 

[swathdiver]

Ohh yeah, the 4.3 was a sbc with two cylinders lopped off. Low rpm, high torque.

 

[iamdub]

Im digging the color of your ride.

Thank you. It's growing on me

 

[iamdub]

Ohh yeah, the 4.3 was a sbc with two cylinders lopped off. Low rpm, high torque.

But, dat LV3, doe...