How come some V-8 racecars weighted less than 2000 lb?

[Big time]

And that was before carbon fiber.
Why can't modern supercars be so lightweight?

How much using security glass instead of plexiglass would increase weight?

How those racecars would behave in a modern crash test?
Although they have rollcages would they have crumplezones? I've heard their bodies only follow an aerodynamic function.

[RacingManiac]

Crash test, sound deadening, NVH concern, warranty/reliability testing....all adds up...

Not everyone is prepared to live with a car with Ariel Atom level of "lack of" refinement....

[Matra et Alpine]

coz racecars dont have any of the things in "supercars".
AND for the race variants they are in formulas where there are weight limits.
Race cars dont anticipate head-to-head collision with unrestrained occupants, so they are designed with different constraints ... and thus why modern race formulas require the use of HANS restraints for the head.
Glas is a LOT heavier than plexiglass adn that last thing you want in a race accident is somethign big and solid, as much as possible you WANT things to shear and break off as it sheds energy AWAY from the part containing the driver thus slowing them down more gently.
Race cars are designed for survivability too and so do have aspects of "crumple zones" and evident in the nose cones of single seaters. Also years ago they mandated that the fonrt wheel axis had to be forward of the drivers feets, thus making that area inherently safer.

[coolieman1220]

electronics. wiring adds up

[kingofthering]

Big engine + rolling chassis + bare minimum to qualify as a "car". That's how it's done.

How old are we talking and what kind? I'm sure if you smashed a newer V8 Supercar into a wall it would fare a lot better than an old factory-built drag special muscle car with paper-thin panels and an acid-dipped body.