Besides cam timing, you might want to check ignition timing, if you pulled the rotor (as in, upgrading doohickey); the Woodruf key aligning rotor to crankshaft may be missing, allowing ignition timing to go amiss.
From your comment, I assume you personally installed the 685 kit; also assume your valves and valve seats are in good condition and adjusted properly.
If the engine rev'd o.k. before the 685 kit implant, and the carburetor was unchanged, no reason you shouldn't be able to spin her up with the big-bore conversion, as far as I can see.
Good luck, and please let us know how you make out.