it is possible to bend the valve just by having the weight of the head on it when it was on the work bench.
do a wet & dry compression test, this will tell u if the problem is with the head or not.
also did u know that both the block & head need to be perfectly flat for a cometic gasket to seal properly as the steel is not as forgiving to any distortion like the normal fibre group a gasket.
unless its a new build & u can deck the block as well as the head then use the reinz group a gasket.