Joth

I got my hands on a set of phase 1 inlet manifold spacers that are made from slabs of alloy, that are an inch thick, (oh sorry, ~26 mm), I have a phase 1.5 motor so I know they will go on, but are they any use other than for physical spacing to fit turbo intake pipe? I understand that spacers made of insulating material serve to lower inlet manifold temps, but does the spacing and increase in runner length offer any benefit?

PICKLE

Not really!. As you said, the main reason for doing this is either to raise the manifold to fit a larger bore pipe underneath it, or to seperate the manifold from the heads, to help decrease cylinder temps etc..

A Synthetic material is usually used for this, to help the heat sink properties. The alloy will conduct heat in the same way the manifold itself will (same material!), so they must be targeted at people who need the extra room, rather than those who are worried about engine temps..