SBM head velocities and there application?

cfm demand = cid x rpm x .0009785 / # cylinders

Or rpm = (cfm x cylinders) / (cid x .0009785)

Rpm = 6,012 for a 408 cid

Min csa = b x b x s x rpm x .00353 / 613.8

2.25" min csa so that's supposed to be the smallest area you have anywhere and that's usually the push rod pinch.

I generally just use my made up one seems to always come close min csa = cid x rpm / 1,100,000, which is 2.22" min csa.

So according to this a 408 making peak around 6,012 rpms needs 300 cfms the pinch area of 2.25" and a port volume of 225 cc with an average csa of 2.77" to have recommended velocity of 260 fps. But with the Trick Flow ports is got an average of 2.34" csa and velocity of 308 fps, which states "high usable port velocity (good hp & tq ) with possible hp loss." So obviously ain't terrible but probably given up some hp if the guidelines are somewhat accurate.

According to this it seems hard to have too little velocity, even 250 fps is recommended minimum say good hp and have go 240 fps where there's torque loss. Which is 234 cc and 243 cc respectively, you'd have to go to 243 cc for 300 cfm where torque becomes an issue.

Now obviously these aren't carved in stone and I'm assuming TFs have a port length of 4.95".

If port length was 5.15" or 4.80" the velocity would be 320 fps or 298 fps respectively compared to the 308 fps I'm going by, makes a difference but it don't change by that much.