I have asked this question before, but I didn't get an answer. Does the stock manifold have a crossmember to reduce sound??? Some people have told me that I might have this in the manifold. I race stock, so any restriction that I can get rid of will help. Can I just use a dremel and cut that out? Thanks for and Information you can give me.

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1989 Firebird Formula L03
Stock except for K&N and Flowmasters. Much more to come.

 

No. A stock exhaust manifold is just a hollow piece of cast iron where the exhaust ports can dump into a common chamber. Exhaust manifolds work as well as they do for off-idle torque because they use the "expansion" principle. The gas comes charging out of the port and sees a wide open chamber to spread out in. That acutally works better at low speeds than headers. As the RPMs increase, the lack of direction causes a lot of turbulence and the stock manifold becomes a hinderance.

With headers, the exhaust slug has to push the long column of gas in the header tube out of the way as it comes out. At higher RPMs, the header pipe can take advantage of the inertia of the moving column of gas to scavenge the rest out and "pull" the intake charge into the cylinder. There is an RPM range at which the pipe "resonates" and that is where headers shine.

Some exhaust manifolds for many GM V8s have a divider for the common center exhaust ports. DO NOT REMOVE THAT DIVIDER! Oldsmobile and some Pontiac exhaust manifolds from the late 60's are desirable because that divider helps those siamesed center ports. I didn't know such a feature was on Chevy V8 manifolds. If it's there, it's O.K.