Quote Originally Posted by Dr. Johny Dodge View Post
with the Lengal plenium I'd consider making the spacer a simple rectangle instead of cutting it to the shape of the gasket - then it would also block the plenium from any "line of site" heat transfer from the exhaust castings below

by nature that polished aluminum can is going to collect and store heat

leaning on the polished fins on a black valve cover shows the difference in heat retension / transmission of polished parts vs black painted ones
If I do one by hand, it'll definitely be a simple rectangle.