Designed for 88'' to 107'' engines with compression ratios from 10.0:0 to 10.5:1 and 100'' and 107'' engines with compression ratios 9.7:1 to 10.5:1Strongest from 3500-6000 rpm for 88'' to 103'' engines and 2500-5000 rpm for larger enginesMade in the USAInstaller must check coil bind, valve to valve clearance and valve to piston clearance.