slant six exhaust manifolds

You want to open the exhaust ports in a way so that the manifold port edges are inline with or slightly larger than the port edges on the head all around, so that there are not any 'steps' for the exhaust air to hit. Of course, then you have to worry over the gasket.....

Chekc out this /6 exhaust manifold article....
http://www.slantsix.org/articles/Sl...n/Slant_Six_Exhaust_Manifold_Installation.htm