Maybe had intake valves too tight during cam break in? bent rods?

I just rebuilt my 54 235. set valves according to Oly's method on this site: http://www.stovebolt.com/techtips/valveadjustment.htm
worked like a charm.

However, my rochester that I had been using forever, I rebuilt it and then it was not happy-couldn't adjust and was seeping out the bottom after the rebuild. The bottom butterfly was wallered out and needed to be sleeved. Why it showed up after the rebuild, I don't know. It was fine before. But check it out. you can get a serious vaccum leak there. And a leak that close to the venturi really screws with fuel atomization.

Build 'em to Drive 'em