[rotorwrench]

A lot of little things can add up to a larger problem. Even if I know who rebuilt an engine, I still wouldn't take condition for granted. I'd make sure it has good compression on all four cylinders. Shake the distributor body and the shaft several ways to see if there is any looseness. Cast iron carb bodies stay pretty straight on the flange over time but the aluminum body Tillotson types can warp & cause a vacuum leak. Any carb can have a loose throttle shaft that will cause a vacuum leak. Loose intake manifold?. All these things can cause up and down rpm fluctuations. Someone already mentioned the GAV rod control or choke/high speed mixture valve control. The mixture can be adjusted at speed but it's a pain to reach over there while driving to do this. Adjusting the timing is not too bad a project once you get the hang of it. The points have to open at the right time or it will be a slug a bug. I just follow the Ford procedure to adjust timing and synchronize the spark control so it can be properly retarded for starting then advanced for running.

Pull the engine through with the hand crank to make sure it has no bearing issues. With no spark plugs installed, it should pull pretty easy. Valves may have been changed to stainless steel from the original steel type stems. I prefer the old steel stems or at least a bronze liner in the guides with stainless type stems. The SS stuff likes to gall if the clearances are too close. You don't need any sticky valves for sure.