Intro to a port job

**1.88 tulip 'as cast' intake flow is**
Cfm@28" temp66/73% humidity
.100 52.7
.200 115
.300 166.4
.400 194.6
.500 187.2

**1.88 tulip initial port work shown w/short turn work on straight wall hump
Cfm@28"
.100 67
200 128.5
.300 186
.400 215
.500 243
Starts to saturate at the typical .530-.550 with it peaking @246
I could work on fixing that.. but these are getting 2.02 valves and I'll save it for another day. I just wanted to have a little fun with the 1.88 stock valve. A 1.94 would make little work to have a nice 255 cfm head... but the way the short turns are cast...you have 2 options imo...1 is to lay it back really far to get the even parting line, the other is to just put a bigger valve in it and you have to lay it back so far. I'm just small talking over a beer now.. anyways ..it's always interesting and fun. I need to do a vid or 2, or live feed er something.
Why does THIS graph of lift progress in gradual increments of flow increase as the valve opens (which we would expect) and then some lift flow numbers have near matching flow for .300 AND .400 with a tremendous taper off (falling flat in flow increase) between .400 and .500 (or something similar)?
THANKS for teaching us!!!