The valves have to be initially adjusted upon firing the motor the first time. However if you put the cylinder heads on, how much did you tighten the rockers initially. Too much and you won't have any compression. The camshaft timing could also be 180 degrees out, this would cause your problem as well. I'd go back to the beginning. Bring no. 1 to tdc on compression and make sure the distributor rotor is pointing to no. 1 cylinder, put it all back together and try again. Check the plugs too, they may be fuel fouled by now with all the cranking and no firing.