I have been reading and watched Engine Masters (best program ever) about carb spacers and their affect on different engine combinations. They have open, divided, four hole, four hole tapered, 1/2", 1", 2" etc. They act differently on single plane/dual plane intakes. At about $50 a pop to buy the cheap ones, I thought maybe I could find out what my engine wants with wood. If you check Summit Racing, many say they are made of wood but now that I went back and checked the details, it says Phenolic wood so I guess it isn't really wood after all.