587 heads

oldkimmer here are just some spec to chew on. Forget about the numbers and just look at the flow differences.
First is bone stock 188 tulp intake valve and lots of carbon on the valve. I'm just going to give the highest flow numbers and lift.( note these heads had some bowl work done on them before but stock 188 intake valve with a standard valve job.)

1.88 valve 200.9@600 lift. That is what my virgin bone stock X heads flow.(un touch aka no bowl work or anything.)

Back cut on 188 valve and clean carbon off of valve 201.8@600 lift

2.02 seat cut in and a 38 top cut 45 seat, and a 60/75 bowl cut [email protected] lift

Ground on the valve guide and clean up the port similar to what you did. [email protected] lift (Note .474 was my cam lift at that time. So i tested at .100,.200,.300 .400 .474.,.500 and .600 lift)

Smooth up the port some more and radioed the 60/70 cut [email protected] lift

Re cut seat with a 35 top cut this time and 45 seat, 60/70 bowl cut and only smooth bottom 70 cut into the bowl. [email protected] lift.

At this point my flow number when in the toilet as my focus was flow at 600 lift and cut sever holes in these head trying to do so.
my notes say that i changed, and tested, 22 more time before i settled for 261@500 and 261@600 lift and moved on to the next intake port
Figured out later, along with many other things, that the chamber was my problem.

Any how, my point to all of this is that a GOOD performance valve job, will get you further, much faster, then any porting in the port. After that it just, nickles and dime in gain, that you loose the next time you go after another.