Hi all I have 408 stroker In a 69 dart.My rocker arms are breaking.My push rods are going through my rocker arms.Can this be that they are to soft.Should I look for old ones to replace them with. It was a crate motor 455 hp
Time to invest in some adj. rocker arms to save your investment(408). I run Pro Magnums rockers on my 408 with Eddy heads and big solid roller cam...never an issue.
Sounds more like a valvetrain stability issue. Broken valvetrain is a symptom in most cases - not a problem. It may be that you only need better rockers but you may also have other issues.
Is this solid or hyd. camshaft ? If solid you dont have enough clearance (lash) . If all is correct with geometry and clearances look to the rockers, check pushrod length also.