Small Block Ford 289-351WValve Springs for Hydraulic Flat TappetValve Size: 1.90"/1.60" Port Volume: 170cc/60cc60cc Combustion ChamberMax Lift: .575"Assembled, Sold Individually Designed for non-emissions 289, 302, and 351-Windsor Ford engines, these direct bolt-on heads deliver maximum performance in the 1500-6500 rpm range for all high performance street applications and our Performer RPM Power Package. Will not accept rail rockers.Note: Aftermarket 289/302 heads including Brodix, Edelbrock, Ford Motorsport and World Products with 1/2'' bolt hole diameters (block is 7/16'' bolt hole), except 397-M-6049-P303 (''P'' style head). Require 350-9680 inserts with 350-8552 head bolt or 350-9680 insert with 070-154-3601. If head studs are desired use.