I baked two 9x2
coconut cakes during cooling both cake shrunk . when i took them out of oven both were little over pan rim few minutes later both shrunk from 2'' to about 1 1/2'' only thing i changed was from sour cream used italian custard . can some one give us a tip what went wrong?

First of all, we want to thank all those who replied back. we baked another batch well same thing happend . here is the recipe we are using . 3 3/4c c flour 3 tsp b powder 3/4 tsp salt 3 stick of butter 3 c sugar 6 egg yolks 1 cup whole milk 1/2 c coconut milk 3 tsp vanilla x 1/4 tsp lor ans coconut oil 1 1/2 c sour cream 6 egg whites one box vanilla pudding , this mix makes two 9x2 + ONE 6X3 baking time 55 min at 350 . when i took them out they were beautiful, BUT within minutes all three sunk, bottom of cakes were 9'' in diameter top bout 8'' diameter, in height went from little over 2'' to 1 1/2 ,just dont know . any info will be greatly appreciated thanks .

Since I am limited on cake chemistry and behavior I have only one thing to offer...have you checked the freshness of your baking powder and soda?

Also, weather often affects cakes...has it been particularly humid? I have trouble with chocolate cake rising enough when it's raining outside.

Thank for your reply. Yes we bought new cake flour new baking powder and new baking soda . Im going to clear my head and try it again hopefully third time is a charm .

If I am reading your post correctly, you used Italian custard instead of sour cream?

If the chemical content of the two ingredients is not the same or similar with respect to fat content, moisture content, acidity, etc, then it seems that the substitution would be the thing most likely to be causing your problem. Baking is pretty complicated chemistry. Just because something looks like something else, it doesn't follow that you can substitute.