Now you can bolt BIG tube headers onto your Small Block Chevy! When using GM and aftermarket cylinder heads with a standard Chevy bolt pattern, you are limited to a 1.75" header tube. Dynatech bolt-on adapter plates let you increase header tube size for maximum power. Dynatech adapter plates are CNC machined from 5/8" billet aluminum, and have square windows machined to aid in port matching. The outer bolt pattern features threaded 3/8" steel inserts. Each kit includes plates and hardware for two heads.