Porting small block 915 j-heads

So , I made a provisional "flow bench".

IMG_10001.JPG IMG_10000.JPG IMG_10003.JPG IMG_10002.JPG IMG_10004.JPG
Just a U tube manometer with water to see what happens
My readings on the ruler was


Stock port

,050" 890 mm 35”
,100" 635
,150" 528
,200" 472
,250" 433
,300" 425
,350" 418
,400" 415
,450" 413
,500" 413 mm 16”

,550" 415
,600" 418

Ported

,050" 890 mm 35”
,100" 570
,150" 470
,200" 413
,250" 395
,300" 383
,350" 377
,400" 372
,450" 370
,500" 368
,550" 364
,600" 364 mm 14”

As I can see it and understand this the stock port stalls at ,450" and backs up.
I also see and understand that something has happened in comparison between the ports and as I can see it´s good so far. Still haven´t done the valve job with bigger valves and angles.

Thoughts ??? (are welcome)