It seperates the upper intake from the lower and provides cooler air to enter as the upper intake isnt as hot. Thats why they call it a phenolic spacer. Its an insulator against heat. Plus the spacer adds extra runner length and therefore increases torque downlow.
OK, the spacer that I used is the 3/8 inch.
It will let the upper manifold clear the coolant temp sensor on the drivers side of the lower manifold and also let the fuel lines clear on the passenger side of the lower manifold.
Hope this helps.
There's a bear in there.
Due to the graphic nature of this programme
listener discretion is advised