Big horsepower 318 builds
Yes and no. It’s a lot of boost. Double the sea level psi into the engine and you now have twice the engine size. 5.3 turns into a 10.6. Now how hard is it to make power with an engine size that large?
The OEM cylinder head for the early engines even ported is behind a modern LS. Sub it out for a better head & add the rest like Rich does and you’ll make power.
The videos I'm referring to are NA.
I think it's down to a number of things, not just one big thing.
My opinion, in descending order of importance:
1. Heads. The LS heads are just newer technology. Comparing cutting edge 2000s tech (ported AFR LS cathedral heads) to even the best available street heads for a sbm, unfortunately, there's really no contest.
2. Intake. That LS3 style intake is apparently VERY good, and seems to work VERY well over a broad rpm range.
3. Cams. The LS cams seem to be pretty aggressive, i.e. for a given duration they have quite a lot of lift.
4. Valvetrain geometry. LS platform addresses valvetrain geometry issues that older engines dealt with. (I'm assuming this ties in with point 3 above)
5. The little things. I'm making some assumptions here, but I'm thinking things like better reciprocating assembly geometry, optimized ring packages, better machining tolerances, more rigid blocks, etc. Maybe these things aren't big but they probably add another 10-20hp to the mix.