Welp, got a doner.

[Astro]

LS engines make their power at a higher engine speed because their design. They also have less displacement. In a heavy truck they really need more gear and more stall speed if they are mated to an automatic transmission.

Like 455s in the back? Man mine are stock 373 with 35's, a 4L80 and a stock converter. It drags already.

 

[0xDEADBEEF]

LS engines make their power at a higher engine speed because their design. They also have less displacement. In a heavy truck they really need more gear and more stall speed if they are mated to an automatic transmission.

I have a theory that the engineers originally planned to use a higher displacement LS vs the Gen I counterpart. The 4.8 was to replace the 4.3, the 5.3 was to replace the 5.0 and the 6.0 was to replace the 5.7. (8.1 already replaced the 7.4.)

But then the bean counters got involved and they kept the 4.3.

Might have changed perception if it went that way.

 

[TonyM]

You haven't even got the donor engine out yet and already L31 express has you thinking you need a cam for it or its useless.

I'm not sure why he has a one track mind hate for LS engines. Maybe another guy in a Van with an LS at the track spanked him in a race? But I have to wonder,,, could there really be 2 vans on any race track at one given time? Do people even race vans? Is that a thing? So many questions

Nobody I know has been unhappy after swapping their sbc for an LS. One thing to remember is that 5.3 is way more capable than a 350, and even a 383. If your planning on hopping it up, it will make more power per bolt on than any sbc would

 

[Deancr11]

It's still a LS is the biggest problem. I know everybody has done everything with the ******** they can think of. I'm just not buying not all the bull poop that it's a this and that. Problem 1 takes a GD computer to make it start and run and the you have to go into it and delete this and change that. Will it last as long as an old school SBC no to much plastic and aluminum lighter crap cheaper made crap. Now I understand stand some of y'all like this computer stuff because it makes it so easy to do this and that with so little chance of getting a little dirty. Now you older fellers can take an old school SBC mix and match some parts do a little machine work. Drop in a distributor get some fuel to it and know. Make adjustments as needed with a screwdriver and 9/16 wrench

 

[L31MaxExpress]

You haven't even got the donor engine out yet and already L31 express has you thinking you need a cam for it or its useless.

I'm not sure why he has a one track mind hate for LS engines. Maybe another guy in a Van with an LS at the track spanked him in a race? But I have to wonder,,, could there really be 2 vans on any race track at one given time? Do people even race vans? Is that a thing? So many questions

Nobody I know has been unhappy after swapping their sbc for an LS. One thing to remember is that 5.3 is way more capable than a 350, and even a 383. If your planning on hopping it up, it will make more power per bolt on than any sbc would

The last paragraph is not even close to accurate.

 

[Erik the Awful]

One thing to remember is that 5.3 is way more capable than a 350, and even a 383. If your planning on hopping it up, it will make more power per bolt on than any sbc would

Not quite true, but also true.

If you're pulling engines out of the junkyard to compare them, the stock LS engines flow better at higher rpm but lack for torque. The SBCs make great torque but struggle for air at higher rpm. The LS engines are good because they correct the two largest problems with SBCs: a relatively weak bottom end, and poor heads. You can address these problems on a SBC, but the LS engine comes with them fixed. That's the LS's selling point.

If you build a 4.000 x 3.750 SBC shortblock and put good heads on it and build a 4.000 x 3.750 LS shortblock with similar flowing heads, they will react the same to any upgrades, and they'll make the same power. The LS will have a slight edge from thinner rings, and that's another thing you can fix in the SBC. The LS will have a higher power capability before splitting the block apart, but that's because of the bottom end, and you can get the SBC closer with a stud girdle.

 

[0xDEADBEEF]

Not quite true, but also true.

If you're pulling engines out of the junkyard to compare them, the stock LS engines flow better at higher rpm but lack for torque. The SBCs make great torque but struggle for air at higher rpm. The LS engines are good because they correct the two largest problems with SBCs: a relatively weak bottom end, and poor heads. You can address these problems on a SBC, but the LS engine comes with them fixed. That's the LS's selling point.

If you build a 4.000 x 3.750 SBC shortblock and put good heads on it and build a 4.000 x 3.750 LS shortblock with similar flowing heads, they will react the same to any upgrades, and they'll make the same power. The LS will have a slight edge from thinner rings, and that's another thing you can fix in the SBC. The LS will have a higher power capability before splitting the block apart, but that's because of the bottom end, and you can get the SBC closer with a stud girdle.

There might be a small difference from the firing order, but you could correct that too.

The SBC torque difference is, in my opinion, due to the reduced flow leading to an increase the velocity. The more you open them up the closer you get to an LS torque curve, which everyone here seems to hate.

 

[Erik the Awful]

I don't hate the LS torque curve, I just don't think it suits a truck.

 

[0xDEADBEEF]

I understand. The SBC just really wants to go without a lot of encouragement. My problem with it is after that.

 

[L31MaxExpress]

There might be a small difference from the firing order, but you could correct that too.

The SBC torque difference is, in my opinion, due to the reduced flow leading to an increase the velocity. The more you open them up the closer you get to an LS torque curve, which everyone here seems to hate.

The more headflow I added to my SBC the more torque it made throughout the whole curve. It is when you overcam the SBC that the curve starts to shift LS like. A 383 SBC can easily make 500+ tq @ 3,000 rpm. You can make 400 ft/lbs practically off-idle with a L31 350. The stock B82 4L80E converter stalled about 2,500 rpm behind my 7395 cammed L31. As soon as I was into the throttle from a stop it had torque.

This is the curve from the 9.1:1 marine L31 with the 7395' 196/206 roller cam. If you run higher flowing heads like Etec170s or even the offshore 200cc heads, adds considerable torque everywhere especially using 1.7 rockers for more lift.

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