Rocker Arms 101

Everything You Always Wanted To Know About SBC Valvetrain Tech But Were Afraid To Ask

Brian Reese Aug 23, 2007 0 Comment(s)
Vemp_0703_20_z 1996_chevrolet_corvette Rocker_arm_installation 1/31

Comp's narrow-body, self-aligning, aluminum rockers can boost the effective valve lift of a '95-'96 LT1 from 0.447/0.459 to approximately 0.477/0.490-more than the vaunted '96 LT4. Additional benefits include reduced valvetrain friction and oil temperatures.

Rockin' Out
A straightforward valvetrain upgrade enlivens our low-buck '96

To help you wrap your brain around all the heady technical esoterica touched on in the foregoing piece, we thought we'd also provide you with a nice, simple, liberal-arts-level installation story demonstrating the real-world effects of a well-planned, properly executed rocker upgrade.

As a test subject, we selected this author's '96 Polo Green coupe, which appeared in these pages previously as the beneficiary of a dollars-down dyno flog, "What Price Performance?" (Nov. '06). In keeping with the budget-conscious nature of the buildup, we asked the valvetrain experts at Comp to recommend a reasonably priced 1.6-ratio roller rocker that would fit the car's factory LT1 heads without modifications. Comp's Chris Douglas suggested we try a set of the company's narrow-body, self-aligning, aluminum units (PN 1016-16), which are designed to fit all '88-up Chevy small-blocks equipped with center-bolt valve covers.

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Our calculations indicated the 1.6 rockers would place our LT1's valve lift uncomfortably close to the rated limit of the factory springs (0.500 inches). To be safe, we upgraded to beehive-style springs, steel locks, and retainers, also from Comp.

While we would have preferred to simply bolt on the rockers and go, our research indicated the LT1's stock valvesprings would be uncomfortably close to coil bind at the lift levels yielded by the larger 1.6 ratio. (A '96 LT1 equipped with 1.6-ratio rockers will generate lift measurements of approximately 0.477/0.490 inches at the valve.) With this in mind, we decided to augment the rocker upgrade with a set of Comp's PN 26918-16 beehive springs, which are rated for lift levels of up to 0.600 inch. This would be more than enough for our stock-cammed engine and would give us plenty of room to "grow into" the higher-lift cam upgrade we have planned for the near future. As an added benefit, the stiffer springs would vastly improve the LT1's valvetrain stability at elevated rpm levels, likely unleashing a few extra horsepower in the process.

Comp steel retainers (PN 787-16) and locks (PN 601-16) formed the rest of our valvetrain package, giving the new rockers and springs a bulletproof foundation upon which to work their performance-enhancing magic. Although Comp offers these parts in titanium, we felt the basic steel jobs better suited our pricing criterion. They should also provide more-than-adequate valvetrain support for our lightly modified LT1.

Finally, since we'd be tearing things apart anyway, we picked up a fresh set of Fel-Pro valve-stem seals from a local auto-parts outlet. For around $20, they seemed like a no-brainer maintenance item for our 10-year-old engine.

For the installation, we once again relied on Seffner, Florida-based Corvette-tuner Anti-Venom. A-V's owner, Greg Lovell, has years of experience wrenching on Vettes of all vintages, so he didn't treat us like a bad smell when we rolled up in our far-from-pristine C4. Follow along as we attempt to wring LT4-topping valvetrain performance and stability from a simple, affordable package.

Sources

Comp Cams
Memphis, TN 38118
800-999-0853
http://www.compcams.com
Anti-Venom
Seffner, FL 33584

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