Some advantages to a LS engine are:
-6 bolt mains
-better oiling systems
-improved power peak
-higher redline, especially LS7, it has been tested to 8000rpm, but doesnt make power after about 7000
The LS engine will make the same power as the old sbc but will do it with a lot less cam. I have seen comparisons done and the LS engine will make the same power and do it with 4 or 5 more inhg of idle vacuum.
Summit is selling a 6.0 liter LS2 that makes 446hp @6200 and 412ftlbs @ 5000 with a very small cam (200/203 degrees at 0.050 with 0.500" lift) for 5300.00. That cam in an old 350 would only make around 325hp @5000 and 400ftlb @3500 and that is with a set of ARF heads. If stock heads where used, it may only make 275hp.
In addition to what has already been mentioned, larger and straighter intake runners. The LS series will prove to be Chevy's greatest engine, but it is butt ugly compared to a traditional SBC IMO. It will never look as good as a traditional SBC in a street rod.
FWIW, The new ZO6 Vette with the LS7 427cid/505hp is the fastest production car Chevy has made to date.
AMEN !!!! it is truly butt ugly, I know theres an engineering reason for it but if they would just move those coil packs off the valve covers it would help alot. And yes they will get with the program, just got back from So. Cal. and a "white nuckler" ride in an old freinds new 505 hp Z06. Now I've been in some fast cars in my life but this thing was THEEEEEEE fastest.
If thats not enough, GM has developed a rumored but said to a real deal limited edition 650 hp vette to be released sometime in the near future, can't even imagine that ride........or how much it will get marked up by the dealers. I bet Leno will get one of the first ones........
The big thing is technology. The computer-aided casting design is so much stronger. A completely stock LS1 bottom end is very capable of giving 100k or more reliability at 600 hp. That same level of reliability in a traditional SBC is more like the 350-400hp mark at best.
The heads use a very different type of intake port that flows much more without sacrificing velocity and therefore torque and drivability. The quality of head flow is what makes such excellent power.
They also not only use those wonderful 6-bolt mains, but they incorporate a stiff cast aluminum oil pan that further stiffens the crankcase.
I guess it all depends on what your looking for.If im looking for good performance,reasonable price,and looks a sbc is a good choice but if u have the money and dont mind going new style in an classic car then a late model LS motor is the way to go.