engine misfire

Q: I have a 402 big block motor in my Chevy truck. It runs great from 1,800-2,000 rpm, on up. It has a Crane RV cam, Edelbrock Performer intake, and Performer heads. The rest is stock Chevy and pretty new (10,000 miles). At idle, it has a bad miss on cylinders 5 and 7 (we put the