You’ve got questions. We’ve got the answers—the Summit Racing tech department tackles your automotive-related conundrums. This week, we’re examining how changing rocker arm ratio can help performance.
T.Y. Thornton, IL
Q: I am in the market for roller rockers. I own a 1966 SS Chevelle with a 396. The engine is bored .030 over, has 10.25:1 compression forged pistons, oval port heads, 290-degree advertised duration/.560-inch lift hydraulic cam, and an Edelbrock Torker intake with Holley 750 cfm Holley double pumper. The engine currently has 1.7-ratio rocker arms.
The car is quick now, but a friend says Harland Sharp 1.8-ratio roller rockers will improved my engine’s performance. Is there any advantage to running the 1.8 rockers versus the 1.7s?
A: Switching to the 1.8-ratio rocker arms will increase your actual valve lift to .590-inch, giving you increased high rpm performance. The downside is that you will lose some low-end torque. If you can live with that compromise, then by all means bolt on the 1.8 Harland Sharp rockers.
For more information on how rocker arm ratio relates to power and performance, take a look at this video from an earlier OnAllCylinders post.