It seems like your timing and jetting are on the money. Since you don't know specs on cam, maybe pull valve covers and check valve lift and make sure everything is okay up there. I just put a 4 barrel manifold on my 318 and it ran terrible. Thought it might be air leak pulled manifold off and found every pushrod bent. Also distributor was missing a clip to hold down advance. Put new rods in and new distributor and it runs great now. Car didn't run that bad with 2 barrel carb, but terrible with 4 BBl.
