5.3 compared to 5.7

[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...