Quote:
Originally Posted by gto_ron
Tom, John
I've been following this thread and the info is valuable. Tom, if the flow is about the same for most of the cast iron heads mentioned does that mean the larger valve sizes in the later heads(670 etc.) didn't really increase horsepower as one would expect?
thanks again for the info, I'm always learning
Ron
64 convertible
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There is a noticeable difference in performance switching to big valve heads. The big valve heads also have guide plates. The pushrod hole on the 1965 heads is smaller, it keeps the pushrod in place. Chevy small block heads of the same era used the small pushrod hole. Later model Chevy heads opened up the pushrod hole like the big valve Pontiac heads.