CL20-224-4 Competition Cam installation question

The motor has too much cam and hardly idles, smells like unburnt fuel because of the cam overlap, and hardly creates enough vacuum for the brakes to work!
The stink might not have been, probably was not, anything to do with the overlap. Big cams have special needs regarding the synchronizing of the throttle blades to the transfer slots, and Idle-timing. And some cams will not work properly at idle with a metering-rod carb, without a lot of work.
You may find a similar situation with your new cam, depending on the specs. And depending on your cylinder pressure, you cannot always install a smaller cam without making other changes. I hope your mechanic knows this and is on top of it.