I have a set of 243s that I would like to clean up before installing on my LS1.

If I were to remove the valves in order to better access the ports while cleaning with a nylon bristle brush and solvent, will they go back in easily? Will they need to be lapped?

 

Whether they need lapped depends on their current condition. Removing the valves and reinstalling them will not change that.

 

Just my .02 cent worth but I would go ahead and lap them while they are out, its not a hard job to do just a little time consuming. As far as reinstalling them it wont be hard as long as you have the right tool for the job.