How to Calculate Cam Lift With 1.6 Rocker Arms


You can calculate advertised cam lift by multiplying the rocker arm ratio by the actual lift provided by the camshaft. Most engines use 1.5-to-1 ratio rocker arms. To get extra cam lift on an engine using 1.5-to-1 ratio rocker arms, install 1.6-to-1 ratio rocker arms. This trick will provide a power increase within the existing power band, where installing a higher lift cam with its associated increased duration would move the power band upward in the revolutions per minute (rpm) range, thereby providing an approximate 6 percent increase in lift. You must know your advertised lift value to calculate your new lift.

  • Record the advertised lift for your stock 1.5-to-1 ratio rockers.

  • Multiply that number by 1.067, which accounts for the difference between the 1.5-to-1 and 1.6-to-1 rocker arms.

  • Derive your new lift from the product of the two numbers. For instance, if your original lift is .45 inches, multiply .450 X 1.067 = .48015, which rounds off to .48, indicating a cam lift of .48 inches.

Tips & Warnings

  • If you already have a big cam (over .45 inch), check your valve springs for "coil bind"---a condition in which the valve opens so far that the valve spring coils hit each other. (You will need a feeler gauge and the valve spring clearance specification for your specific engine to check for this condition.) If you encounter coil bind, you will need high-performance valve springs with thinner coils.

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