screw-in rocker arm studs bolts on to 1987-94mustang engines with no loss of ... material high density cast iron valve seats integral intake hardened steel exhaust ... guides integral cast iron valve spring seats machined for 1.250/1.550 springs ... plugs accepts 14mm .460 reach tapered seat 5/8 hex champion #670 or #802 or ... /32 spring specs bare 1.250 single 100 seat 1.437 dual 125 seat bare 1.250 single ... 100 seat 1.437 dual 125 seat max lift chamber 64cc .560 64cc .600 ...