I've got a similar issue with the 1955 235 that I've got in my 1951 Chevy 3100 5-Window. I've got Fenton dual intake and two Rochester carbs and I'm having a heck of time trying to get these things synced up. I'd almost bet your issue is carb related as is mine. Search the forum for Rochester Carb rebuild and I'd almost guarantee that you'll find someone that has documented this. You could also use
www.google.com and search for Rochester carb rebuild. Best of luck!
