If it has a new flat tappet camshaft, the lobes are soft . Breaking in the camshaft is done to work harden those lobes.. A little like forging a part makes it stronger. We use to run them at about 1500 rpm for 20-minutes with break-in lube on the lobes. That helps work harden the camshaft's lobes and seat the lifters to the lobes. If you do not break-in the cam the lobes can wear away and go "flat" and your valves will no longer happen. After the cam is broke in you want to drive it around varying the rpm, this changes the load on the rings, and helps them break-in. I remember there were different procedures for different types of rings but I don't remember what they were. Everybody use to say not to drive the vehicle over 50 mph for the first 500 miles. I'm not sure that really matters? Then you change the oil after 500 miles to get the break-in lube out of there and any junk floating in the oil that might have been from the machining and assembly process (there should not be any unless your a hack builder). Right now the best oil to use with flat tappet cams is oil designed for diesel trucks. They still have to put all the good anti-wear additives in that oil because of the extreme pressures caused by the high compression ratios. I suggest Delo 15W40 diesel oil if you have a flat tappet camshaft. Walmart is the cheapest.
You want the engine to start immediately and run it up to 1500, maybe even 2000 rpm. I'm not sure which it is, its been over 20-year's since my last engine build. You do not want not to be fussing around with the timing trying to get it to start or cranking it to fill up the carb.
Most guys spin the oil pump driveshaft to bring the oil pressure up. Also fill the oil filter up before spinning it on. I had one 289 that would not prime? I had primed the oil pump before assembling it to the engine? I pulled the oil filter off and took an oil squirt can and jammed it up in the block through the oil filter adapter and back filled the oil pump with more oil. After that it, it primed and started pumping, Stick the distributor back in and use a timing light while just cranking the engine with the key on. You don't want any fuel in the carb yet because you don't want it trying to start. The timing mark will light up even though your just cranking the engine. That will tell you if you have the distributor in correctly and the timing is close to where it needs to be before you start the engine. 10 degrees is a good starting spot. Later on you can go back and reset the timing because it will probably change with the higher running rpm. Now Pre-fill the float bowls with fuel if you have an electric fuel pump. If not, I use a little tiny funnel made for Radio controlled toy car gas tanks. I fill the bowls through the vent tubes. If you have a Holley you can pull the site plugs and fill the bowls to the bottom of the plugs. Move the carb linkage until you start to see the accelerator pump start squirting. Give it several squirts. It should start up in just a couple of rotations. Don't worry about adjusting the idle rpm or anything except turning the idle speed screw to run the rpm up to the manufacturers suggested rpm for breaking in the cam and let it run for 20-minutes. Watch the temperature and oil pressure and check for leaks. Afterwards set your timing and idle a/f mixture and go for a ride.
Always set points first if you are using them. Then the timing and last the air fuel mixture. It has to be dome it that order. That is because dwell (point gap) changes the timing but timing does not change the dwell. Timing effects the fuel mixture but the fuel mixture does not change the timing. That is why we adjust the carb last.
The very best way to do adjust the carb is with a little propane bottle. I should have mentioned this before. Before you try and start the engine lightly bottom out the A/F mixture screws and back them out 1 1/2 turns so that they are all set exactly the same. After the engine is broke in check your fuel float level , set that first before any carb adjustments. Run the propane bottle over the carb while its idling. You can use starting fluid or carb spray with just a light spray but the propane bottle is the hot ticket. If the idle goes down that means the engine is already too rich and it could not handle any more fuel. If the idle goes up with the propane the engine was too lean and it liked that extra fuel you were giving it. You make small adjustments, 1/8 turn at atime to all the A/F screws at the same time keeping them all turned exactly the same amount. When the idle does not change with the addiction of a "little" propane you are real close to having it set perfect.
Because an old fashioned carbureted engine cannot make air fuel adjustments for temperature and atmospheric pressure changes (they run different on a cloudy day or a different altitude) like modern cars you set the air fuel ratio a little to the rich side to compensate for that stuff. Maybe an extra 1/4 of a turn out on the air fuel mixture screws from where you had it set with the propane.
Later on you will want to dial that carb in with the correct jets, power valves and accelerator pump settings. It will make a big difference in how your engine runs and what kind of gas mileage you will get. Another lesson for another day.
