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I'm in the process of building a 4.6 DOHC mustang engine that will have 14 pounds of boost. I'm in the process of porting my heads (first time) and wanted to smooth out the intake port and valve bowl area to remove any high spots (sanding only). On the exhaust ports I wanted to open them up a little bit without losing velocity. My question is after removing a slight amount of material on the exhaust ports I flared the the port slightly to where it meets the exhaust gasket size instead keep it straight or port matching. How will flairing out effect performance on an exhaust port and did I just screw up? I've attached pictures and please give me your feedback and advice.
Thanks for your help!
what you have done there will not drop any power the outer lip there does not have much bearing on the power the exhaust port on these heads is quite small from memory and does gain by doing the cleaning up that you have done further in the port the main area of advancement is gain just under the valve and up to the valve guide area, by opening this up about 3mm and smoothing the inner radius you will see a gain, also the same areas on the inlet side
Because I'm not familiar with those heads, and cylinder head design varies so much, I was trying to find some info' on them. It seems there are some different details used over the years and you may find this of interest. https://lateral-g.net/forums/showthread.php?t=6999
As Ross said, the seat shape - both head and valve - and the first inch, or so, of the bowl and port, can play a big part in gas flow, especially with lower lift camshafts but it's also quite important for the rest of the ports, too. There are quite a few on-line 'porting' guides and videos, you may wish to check some out to see how they apply to your engine.