440 breaking up at 5600 RPM

I had the same exact problem and then i broke a valve and toasted a 15,000 dollar engine turns out those rocker shafts from 440source were not hardend right and the bearings on the rockers ate into the shaft i chased jets electric ingintion etc for months before it finally dropped a valve please do yourself a favor and check those rockers and shafts if you are using the 440 source stuff so you dont end up like me