blis

If you have pulled down the engine, rebuilt it and it has good compression.
Ensure you have ample fuel pressure and no air leaks anywhere in the system, specially exhaust and tank nipples. If you are certain there is fuel flow, you have compression and you have a spare new plug on hand. Check your starter with spare plug.

1. Set IDLE gap, looking down carby throat to 1mm.
2. Setup your linkages and servo subtrims and put a rubber band between carby linkage and top needle.
3. Unwind top need 1-2 complete turns to open up maximum top fuel pressure*(you wont be revving until you sort out the idle mixture)
4. Glow Spanner handy, prime the car with three good pulls or blow into pressure tube. Attempt to start it, if there's no sign of ignition, remove the plug, "unflood" engine by turning it over and observe the mix comping out of the engine.
   
5. Lean the bottom mixture some more, try starting again. If no combustion, go back and unflood. (It's never nice to screw a NEEDLE all the way into a SEAT, so dont go too far ok!) Keep repeating until you get a puff and then lean bottom 1/4 turn more and it should fire.

A good race tune will stall an idling engine in 4 or so seconds. If you really feel it needs more idle/air then consider that it also changes the mix when you do. From there, lean the top on the bench until it stops choking and put on track for a warm-up before final tune.

I believe any decent cold engine can be started, even shagged one's will start and then flame out through lack of compression when hot. But.. If it's sucking air in via bearings, boots, seals or carby, it's just not worth trying.