Cutting up a head is a good reference,just remember all heads are not the same so there are core shifts.
Meaning, just beacause one cyl head you can install 1.9" valves & not hit the water jackets does not mean you can do the same on another head.
Just be safe on what size intake valves you install,I installed 1.90 intakes on my 194 Cyl head,w/no problems, you can put 1.88" valves(cut down 1.94 Chevy valves )or even 1.85" would be fine ,to be safe.
Some people put 1.94 valves in,but that shrouds the intake valve & you will need to open/unshroud the combustion chamber to get it to flow good.
I say 1.90 -1.88 to play it safe. But that's just my opinion,ask Larry T6 what he thinks for a safe size valve to use,he also has a lot of cut up heads to go by.
I will try & find some valve grind angle & seat angles when I get a chance.
But,,, since you are in Brazil,, & inline Chevy sixes seem popular, I think a cylinder head shop there should know something,,,maybe?
Just, remember ,when porting, do not make your intake any larger(for the most part)
You are trying to bring the intake port volume smaller, not bigger.
It's mainly about the bowl areas,short turn & long turn radius's & the entry just below the valve seat area, Bernoulli's principle.
MBHD
