quote:Originally posted by PanteraDoug:Granted I am not an engine builder but I don't understand the rational of squaring up the exhaust port, then making a transition piece to a round exhaust tube.
Kelly. Do you understand the thinking on that?
No, not really but not to let that get in the way and just thinking out loud, I'd say it was possibly done to increase the cross sectional area to further the flow potential of the port in a critical area. Sometimes it’s because of the porting constraints of the casting wall thickness but more likely because of the dimensional constraints of the port because I suspect there’s plenty more meat to port there.
A square cross section has about 21.5% (square not rounded corners) more area than the largest circle that fits within the square and this happens to be at the location where your trying to turn the exhaust flow as it exits the port so it may produce a similar effect to having a more gradual radius or higher round port. Once you’re outside the head your less constrained and practicality says you go back to bending round tube for headers.
Of course it assumes the entire cross section remains active and the transitions are such that flow doesn’t become turbulent or suffer other disruptive losses…..someone must have thought it worked. Same reasoning likely applies to intake port shape.
Best,
K