Proform 66913C Chevrolet big block aluminum roller rockers. 1.7 ratio. Use with 7/16" studs. Works on 396, 402, 427, 454, and 502 Chevrolet big block engines from 1965-1990. Rid your engine of internal friction with roller-tipped rocker arms. The race-proven full needle bearing, fulcrum and roller tip not only unleash horsepower, they also lengthen valve train component life and reduce wear and tear on valve stem tips. Precision machined to insure consistency and ratio accuracy. Sold as 16 extruded aluminum roller rockers and 16 poly locks. Proform 66913 396 402 427 454 502 roller rockers PROFORM-66913C Check out our selection of Chevy big block rocker arms ! HOW TO ORDER: 1. If there is an applications box, click, then scroll the applications box to find your vehicle. 2. Click on your vehicle. 3. Click "add to cart" 4. Enter your information and submit order. 5. If there is no applications box, then just click "add to cart", then enter your information. HOURS: 11:00 am to 6:00 pm Monday - Friday Eastern Standard Time We welcome CANADIAN customers! For ordering information, click on "Orders To Canada" at the top left side of this page. We will not ship to freight forwarding - expediting companies. PAYMENT METHODS: PayPal, Visa, Mastercard, Discover, American Express, money orders.