I'm in the process of building a 408 out of a 2008 lq4 block and I've got the crank in but I'm yet to install the rods and pistons. It just crossed my mind I may need to clearance the bottom of the cylinder walls. I know I'll have to space out the windage tray but should the block need to be clearanced?

 

Clearance grinding will be needed. Pretty sure that's why Tony Mamo uses small journal (2.00") cranks for his stroker combinations in order to minimize or eliminate the grinding needed.

 

If it's like my LS1 stroker the clearancing is pretty minimal depending on which rods were used. Just install one piston/rod and you can see where it comes close or hits. I had the machine shop do mine when they honed the cylinders and balanced the rotating assembly and they charged me something like $50

 

Iron blocks usually do not need clearancing due to their shorter cylinders, my LY6 block did not require clearancing. The only way to be sure is to measure.

Good luck!