i have a b18b1 engine that im currently gonna replace the headgasket i took the head off already and i notice a small scratch on one of the cylinder walls i honed the walls but i can still see the little scratch and was wondering if thats a sign of a cracked block

if its a crack you would have a milky brown liquid in the radiator and around the cylinder walls a scratch then either metal from your pan or some how got stuck between the piston and wall and scratched it. that scratch may give you some oil blow by and a lose of power because of the oil getting by the rings and do a leak down and compression test if possible to see how it all comes out. and also after time the combustion area will turn black from the oil getting by and may cause other issues for you so if u dont bore it out more then keep an eye out on it and test every once and a while to make sure its not doing anything to the motor

thanks and i hear of people saying that when they repleaced headgaskets they put rtv or some other kind of sealer i was wondering if thats a good idea or if i should just install it with out any sealer

dont use sealer with the head gasket it doesn't need it. the valve cover does in all the corners not a lot just a little. just remember that u need a new head gasket when u take if off its always a good idea and if you don't it may leak later down the road sooner then it needs too.