After
Max torque: 550 lb-ft @ 4,000 rpm
Max power: 502 hp @ 5,500 rpm
Average torque: 517 lb-ft
Average power: 394 hp
Difference
+ 32 lb-ft
+ 50 hp
Centrifugal Supercharger
The Bolt-On
Vortech Superchargers standard smallblock carbureted kit with a V2 S-trim compressor running 5.5 pounds boost, along with a mighty Demon 750-cfm blower carb. $3,500
The Mule
A '69 Nova with a bone-stock 350 lower end, '70s-era open-chamber heads with 1.94/1.50-inch valves, an edelbrock Performer intake, a Holley 650-cfm vacuum secondary carb, and a Turbo 350 transmission. Power measured at the rear wheels.
Our Take
Even on this very tame engine, the Vortech blow-through setup increased power by almost 50 percent at the wheels; we calculate the gain at the flywheel to be right about 100 hp, which shows that even a small blower setup can produce big gains.
Before
Max torque: 222 lb-ft @ 2,300 rpm
Max power: 131 hp @ 4,100 rpm
Average torque: 165 lb-ft
Average power: 106 hp
After
Max torque: 278 lb-ft @ 2,600 rpm
Max power: 194 hp @ 4,300 rpm
Average torque: 214 lb-ft
Average power: 150 hp
Difference
+ 56 lb-ft
+ 63 hp
Roller Rocker Arms
The Bolt-On
Lunati Voodoo 1.6:1 roller rocker arms.$338
The Mule
A bone-stock '70 chevelle SS convertible powered by an RPO L65, 9.0:1-compression 350 small-block, which came factory rated at 250 gross horsepower and 345 lb-ft of torque, running through a Turbo 350 trans. The only modification was a 21/2-inch dual exhaust system with turbo muffl ers. Power measured at the rear wheels.
Our Take
Some of the increase undoubtedly came from the extra lift provided by the rocker arms, but Lunati's James Humphrey told us most of the gain likely came from the decrease in valvetrain friction achieved by installing full roller rockers in place of the factory stamped-steel pieces.
Before
Max torque: 258 lb-ft @ 3,400 rpm
Max power: 187 hp @ 4,200 rpm
Average torque: 242 lb-ft
Average power: 171 hp
After
Max torque: 265 lb-ft @ 3,400 rpm
Max power: 194 hp @ 4,200 rpm
Average torque: 247 lb-ft
Average power: 173 hp
Difference
+ 7 lb-ft
+ 7 hp
Intake Manifold
The Bolt-On
We followed up the rocker swap with an edelbrock Performer dual-plane aluminum intake. $120
The Mule
The '70 chevelle now fitted with the Lunati rocker arms. Power measured at the rear wheels.
Our Take
The Performer intake flows more air than the portly factory iron piece. Equally important is that its more modern design evens out the airflow between cylinders. Both factors lead to a nice increase in power.
Before
Max torque: 265 lb-ft @ 3,400 rpm
Max power: 194 hp @ 4,200 rpm
Average torque: 247 lb-ft
Average power: 173 hp
After
Max torque: 278 lb-ft @ 3,800 rpm
Max power: 211 hp @ 4,100 rpm
Average torque: 267 lb-ft
Average power: 189 hp
Difference
+ 13 lb-ft
+ 17 hp
Carburetor
The Bolt-On
Rocker arms and new intake in place, we replaced the chevelle's original Quadrajet mixer with a 525-cfm Road Demon vacuum secondary carb (64/78 jets).$357
The Mule
The '70 chevelle now fitted with the Lunati rocker arms and edelbrock intake manifold. Power measured at the rear wheels.
Our Take
This was a tough one-Demon recommends its carbs for modified engines, not a factory cammed, low-compression stocker like we flogged here. Although peak gains were minimal, average power was improved through the powerband. This carb also gives us a good, easily tunable foundation to work with as more extensive modifications are made to this engine.
Before
Max torque: 278 lb-ft @ 3,800 rpm
Max power: 211 hp @ 4,100 rpm
Average torque: 267 lb-ft
Average power: 189 hp
After
Max torque: 282 lb-ft @ 3,400 rpm
Max power: 212 hp @ 4,100 rpm
Average torque: 272 lb-ft
Average power: 192 hp
Difference
+ 4 lb-ft
+ 1 hp
Dyno Thrashin'
Headers
The Bolt-On
Doug's Headers with 15/8-inch primary tubes and 3-inch collectors. $530