Roller Rocker Arms
The bolt-on
Comp Cams Pro Magnum roller rocker arms, 1.6:1 intake and 1.52:1 exhaust. $276
The mule
An out-of-the-crate ZZ4 350ci small-block: 10:1 compression, GM dual-plane intake and aluminum 58cc heads, and a Holley 770-cfm carburetor. Power measured at the flywheel.
Our take
The mildly cammed ZZ4 responded to this rocker arm upgrade; if you have one, this mod's a no-brainer.
Before
Max torque: 390 lb-ft @ 4,200 rpmMax power: 344 hp @ 5,200 rpmAverage torque: 371 lb-ftAverage power: 287 hp
After
Max torque: 407 lb-ft @ 4,200Max power: 366 hp @ 5,400 rpmAverage torque: 386 lb-ftAverage power: 302 hp
Difference
+17 lb-ft+22 hp
High-Flow Air Filter
The bolt on
A K&N high-flow air filter. $40
The mule
A 406ci stroker small-block running 11.1:1 compression, Dart Pro 1 227 CNC heads, a Victor Jr. port-matched manifold, and a 750-cfm Mighty Demon carb. Power measured at the flywheel.
Our take
Running a good, high-flow air filter doesn't hurt performance compared to running an open carb.
Before
Max torque: 533 lb-ft @ 5,000 rpmMax power: 583 hp @ 6,300 rpmAverage torque: 485 lb-ftAverage power: 431 hp
After
Max torque: 536 lb-ft @ 5,000 rpmMax power: 582 hp @ 6,300 rpmAverage torque: 488 lb-ftAverage power: 433 hp
Difference
+3 lb-ft-1 hp