I'm about to install the a new head onto my block. G54B / 2.6L. The block has been head-less for a couple months with the Montero outside so I want to thoroughly clean the deck and combustion chambers.

I'm using a rag and a little WD40, following up with a wipe down with some motor-oil on a rag for the cleaning.

Should I be worried about any possible debris/particles that might have fallen into the coolant passages through the top of the block? If so, what is the best way to go about flushing?

I imagine the easiest way is to let the water pump do the work after the cooling system is back together, but would I be better off doing this earlier to prevent cycling any foreign matter through the cooling system?

Thanks all!