440 breaking up at 5600 RPM

Whats running voltage : At the alternator battery positive post,Ford starter relay, and running voltage,back at the battery...Running voltage,at least:13.8-15.0 ..(How old,is the battery?) Check the cheap basics first, unless you know already....
Brand new Optima yellow top. Haven't checked voltage yet but I was just assuming it was good. Will put the meter on tonight.