xrwagon":1d0pccax said:
thanks mate for the info, i spoke with a crossflow guy today his head flows 390, that is the apparent max so the classic inline head is doing very well when compared.
Thats about the 254 to 257 cfm at 28 "H20 is what I've seen although there are reputed 275 cfm versions which flow 422 hp with gasoline and 597 hp with N20.
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To cut an X-flow head to get 250 cfm plus, you have to have the templates or a flow bench, or find a supplier who says they can make those numbers, and then do independent testing to prove it.
I've gone over all the head flow figures for another project I've been consulting for a Kiwi building a special engine, and its not all about peak cfm at 550 or 600 thou lift and the biggest valves, but things like having the right port and chamber surface texture, good plug placement, short turn radius, paddle wheel mixture motion and finding the smallest port and intake runner capacity to do the job. Ported heads often are disasters with respect to surface texture, and they may make flow bench numbers, but loose out on the brake specific fuel consumption figures. Engines with exhast heating like our non cross flows aren't bad at all for street operation.
http://www.wallaceracing, the Pontiac site, covers off the minimum Pipe Max sizes to make power, and Stan Wiess site accessed from Kelfords Camtech shows all the other calculations. The rest is just finding the right cam to suit the head flow and match that to the old Weber venturi sizing and maximum port sizing to ensure there are no f-ups. Having isolated runners gives you 5 to 10% more power, since the flow figures for cylinder heads don't always include the intake maniold, unless of course they are our beloved log heads.
Anyway, my closing statement is that Mike did the best job on the Classic Inlines aluminum head, and its got the right mix of mixture motion, port area, runner volume and valve size and plug placment to flow one third more air than the best cut-off log, and that ported 231 cfm at 28 H20 is just the start. Its like aero testing a carbody, you can spend 400 hours on any thing with a wind tunnel or flow bench, and a good technician, and you'll get solid gold improvements without any apparent visual differences. Any stock iron or alloy head casting Ford production ports will start off being at least 30% down on the Classic Inlines head at the same lift, and thats a potential 80 hp off the table right away.