Hard to say without a little more info. Connect a timing light to it and find out where that is. If nothing else, at least you'll know what you have the timing set at. To check for a vac leak, you can start the engine and take a small propane torch, turn the gas on (don't light it) and run the nozzle around the base of the carb and intake, if the rpm's pick up while doing this you have found a vac leak where the nozzle is pointed.

Now as for more info...After adding the new parts did you make any adjustments to the carb? Was the bottom end re-built when you were adding the new cam, heads etc? If so, how was the motor, and the cam for that matter, broke in? One last thing I would suggest for now, is that you do a compression check...especially if the bottom end wasn't rebuilt.

Good Luck,
Dutch