Offenhauser 4bbl intake value

You can use the Offy with a stock exhaust manifold. In my opinion, headers would be better performance-wise, but for street applications, it is beneficial to have the manifold heat (especially in colder climates). The factory exhaust manifold will flow quite nicely with a little porting, mostly to open up the size of the outlet to 2 1/4 -2 1/2 inches.