My Old

Below is the hood that came with the car. 

Referred to as a "Cowl Induction" or Chevelle SS hood.

Then I tweaked it...

A new Holley 600 cfm 4-barrel carburetor replaced the old Rochester 2-barrel. 

It came standard with a manual choke.

Under the four-barrel was an Edelbrock Performer (OEM style)

aluminum intake manifold.

I installed a medium performance street cam with about 210 ̊ duration and a .440" lift in a friend's garage.  The design range was from idle to 5,500 rpm and gave an impressive amount of mid-range torque for a mostly unchanged low compression short-block with two-barrel carb setup.

Don't forget the sound system... 

Final modification was a change-over from the existing single exhaust setup to a new dual exhaust glass-pack muffler system.  The early 1970s GMs were still part of that pre-catalytic converter era of cars, making this modification easy and less costly.

The engine's original cylinder heads and bottom-end remained untouched.  Taking this into account and dyno tests with similar engines, the estimated power increase was probably around 14% translating to 280bhp and about 380lb/ft of torque.  (It did smoke tires.)

A friend remarked that it sounded, "healthy," during our convoy to a Council race through Southern Wisconsin.  When I tromped on the accelerator, the transmission down-shifted, it got up and galloped, emitting a loud rapping noise from the new dual exhaust system. 

This '71 Chevelle Malibu could have benefited greatly from better suspension.  It had a marshmallow ride.  The car squatted down considerably more on its rear springs following the power upgrades.

It was a fun car to own and drive only after re-tuning it.  I sold it in 1986 after body rust took over.  That's what happens when you buy a car with a cheap paint job and body filler.  (Think I paid $1,200 for it.)