hosting - Do I need gaps in a pile of rack servers with no rack cabinet? -

i have seen do need leave gaps in standard server rack? , question similar different:

i have several rack servers (dell 2850 mostly) not have rack structure. can put 1 server on top of without having cool issues? (a pile of servers without putting them in rack cabinet, on top of desk 1 above other)

i know rack cabinets allow space between servers, if dont have gaps between them. asking put 1 on top of other, no vertical space @ all.

thanks

yes, designed vent front , rear. stacking them not going make them hotter or cooler if in actual rack.