i check the intake as Cab and others have said, and also use a smear of grease on the head side, and silly-cone one the china walls, big and small block alike.
when using the silly-cone of your choice on a small block, make sure the wall "guide pins" for the gasket are removed, as this will make sure your intake doesn't bottom out on the ends, thus not allowing it to fully seal on the heads.
just an old geezer spilling his experience with a small block intake leak he couldn't find. ............. [as my old man uset'a say : Back up to an A$$kickin' machine with a bag full'a quarters and start shovelin' 'em in !" ]