All too common LS swap vs unique old school small block

[0xDEADBEEF]

You can believe or not believe makes no difference to me. I had my Express on the dyno when it had a stock L31 block that had a 395' cam in it, with a tune, custom 4" air intake and shorties. I also had a 4L85E and GM 14 bolt 9.5". Not 5 minutes later a Vortec Max 6.0L went on it. The 6.0L had an intake, full exhaust including headers and a tune. The old 350 put down 310 tq at 3,100 and 257 hp at 4,900. The 6.0L put down 291 hp @ 5,400 and 299 tq at 4,400. Down at 3,000 rpm the LQ9 6.0L was nearly 50 ft/lbs off the L31. The L31 made more torque than the LQ9 over 1,000 rpm sooner, despite being less cubes and having to spin an 85E rather than a 65E. L31 was also spinning a very large duramax clutch fan and the LQ9 had factory electric fans.

Unless you don't believe GM, it's pretty well settled what the LS2, LQ9, and L31 make.

 

[Erik the Awful]

Unless you don't believe GM...

That's an apples vs oranges comparison. The LO5s and L31s were hampered by GM's unwillingness to make power at the time. Are you seriously comparing the LO5's .382" and the L31's .414" lift to the LS2's .524" and the LQ9's .467"? Take a junkyard 350 and 5.3 and do a complete rebuild on them, along with a mild cam upgrade, and when you're done the 350 will make similar power, but cheaper. The LS' advantage is when you crank the power to eleven. It can withstand power that a 350 can't make. If you're short of that, a 350 is very viable.

For all the kids who don't know what it means to "go to eleven".

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[0xDEADBEEF]

That's an apples vs oranges comparison. The LO5s and L31s were hampered by GM's unwillingness to make power at the time. Are you seriously comparing the LO5's .382" and the L31's .414" lift to the LS2's .524" and the LQ9's .467"? Take a junkyard 350 and 5.3 and do a complete rebuild on them, along with a mild cam upgrade, and when you're done the 350 will make similar power, but cheaper. The LS' advantage is when you crank the power to eleven. It can withstand power that a 350 can't make. If you're short of that, a 350 is very viable.

For all the kids who don't know what it means to "go to eleven".

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Somebody doesn't believe GM's torque numbers. It wasn't my comparison. You can build just about anything to make power.

 

[L31MaxExpress]

Unless you don't believe GM, it's pretty well settled what the LS2, LQ9, and L31 make.

LS2s aren't exactly cheap to find. For what it would take to buy a 150K or more mile LS2, I can build a healthy 383 out of a used L31 and add good aftermarket aluminum heads.

I know what my L31 made with tuning and a couple simple bolt ons even when it was still a stock longblock. I watched a LQ9 with the same mods and it was also tuned dyno not 5 minutes later and the results were as I mentioned above. The L31 made more torque than the LQ9 and did it 1,000 rpm sooner in the powerband. Lower in the powerband where I spend 95% of my time running it was not even a comparison worth making. The L31 killed the LQ9 down in the 2,500-4,000 rpm range by as much as 40-50 ft/lbs in places and that was spinning a driveline that eats more power.

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[0xDEADBEEF]

LS2s aren't exactly cheap to find. For what it would take to buy a 150K or more mile LS2, I can build a healthy 383 out of a used L31 and add good aftermarket aluminum heads.

I know what my L31 made with tuning and a couple simple bolt ons even when it was still a stock longblock. I watched a LQ9 with the same mods and it was also tuned dyno not 5 minutes later and the results were as I mentioned above. The L31 made more torque than the LQ9 and did it 1,000 rpm sooner in the powerband. Lower in the powerband where I spend 95% of my time running it was not even a comparison worth making. The L31 killed the LQ9 down in the 2,500-4,000 rpm range by as much as 40-50 ft/lbs in places and that was spinning a driveline that eats more power.

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No they aren't cheap, nothing is cheap these days. I got my last 6.0 for $800 but that was 7 years ago.

Roller dyno measures torque at the wheels. We know it makes 380 ft-lbs with all the accessories on the engine dyno. Things like big wheels/tires absorb that torque and it won't be measured. You also have a sample of one.

I don't really care about down low power, if I'm doing my job right I'm not spending time there. I'd rather have a flat torque curve out to 6500 rpms or even higher than a lumpy one that comes on earlier.

 

[L31MaxExpress]

No they aren't cheap, nothing is cheap these days. I got my last 6.0 for $800 but that was 7 years ago.

Roller dyno measures torque at the wheels. We know it makes 380 ft-lbs with all the accessories on the engine dyno. Things like big wheels/tires absorb that torque and it won't be measured. You also have a sample of one.

I don't really care about down low power, if I'm doing my job right I'm not spending time there. I'd rather have a flat torque curve out to 6500 rpms or even higher than a lumpy one that comes on earlier.

I guess I will just say, could care less what happens over about 6,200 rpm. My 383 makes a big flat torque curve from 1,500 to about 5,600. Its pulling over 1.00 gm/cyl on the cylinder air value in that rpm range and peaks around 1.14 gms/cyl. Pulling a peak of 422 gms/sec airflow at 5,600 rpm. I'll take a big fat torque curve that is around 500 ft/lbs peak and just stays flat above 450 for 1,000s of RPM over peak hp any day of the week. As I said I spend 95% of my time between 1,500 rpm and 4,500 rpm. My converter stalls at 2,800 rpm and my 383 is already making close to 500 ft/lbs there. I'll take grunt over noise anyday of the week. Less engine stress and less wear for the long haul.

 

[L31MaxExpress]

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I am moving weight and pulling the frontal area of a shed, I'll take the torque vs the noise of a LS on perpetual top-end charge.

 

[0xDEADBEEF]

I'll just finish with the LS was designed to spin and take advantage of what happens with higher rpms. It has 6 bolt mains and a smoother firing order than the SBC for that reason. I could not care less what you could care less about, but I don't mean that to be harsh. You're stuck in your ways, fine, but there are other ways out there.

 

[L31MaxExpress]

I'll just finish with the LS was designed to spin and take advantage of what happens with higher rpms. It has 6 bolt mains and a smoother firing order than the SBC for that reason. I could not care less what you could care less about, but I don't mean that to be harsh. You're stuck in your ways, fine, but there are other ways out there.

I am good at selecting and building combos, good at modeling engines accurately for comparison purposes and nailing down combinations and even have a modified 6.0L in a vehicle. It runs good, but the 383 makes more grunt everywhere. Lloyd Elliot did the heads on both, they flow similarly and they have fairly similar cams that were both ground to have lots of torque production. SBC has slightly less lift, a tighter LSA and more advanced ICL. The 6.0L has a 1/2 point less compression. In real life it takes ~3,000 rpm to get the LS to have the same grunt the 383 has at 1,500 rpm. Its easily apparant even in the datalogs the 6.0L just does not move the air down low that the 383 does. Truth be known the 6.0L doesn't move as much air anywhere as the 383, but it is 19 cubic inches smaller.

383

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6.0L

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[Wh4t3v3rs]

Does anyone here have any experience building race motors? I’ve been doing a little research on big bore short stroke engines for high rev engines for road course and stuff. Is this feasible for the LS in a somewhat affordable manner?

You can de-stroke an 6.0l Ls and it likes to rev to 8k+ rpms.