Our stock cylinder heads are a pertinent piece to getting your car to run correctly. We offer bot h the single port head and dual port heads. out single port head will fit all 1966-1970 1300cc-1600cc engines. The single port heads come installed with the valves already. The springs are also brand new and installed. Our dual port heads are one of the most popular item we carry. They come equipped with quality stainless steel valves for both the intake and the exhaust. Intake vales measure at 35.5mm while the exhaust valves measure at 32mm. If you are questioning whether or not one of your valves is going bad, we highly suggest you replace both of them. This will eliminate any question in whether or not the CC's match or not. While messing with the heads, it doesn't hurt to replace the valve covers and put new clips and gaskets. Let us know if you have any questions.