Nobody can accurately tell you how tight ................
Tight Is

OR
That is too ... Tight or Loose
At long distance and over these pooter screens
Its kinda like finding zero lash .............
Its a show me thing
BUT
Your basic objective is to ...................
Compress the gasket a bit
and
That amount is sufficient
Some go too far beyond that point and do thread damage

Very easy to do on Aluminum Heads I might add
Some believe ... more tight is necessary cause they've lost bolts
thus
They then get involved with the above issues
Bottom line on header bolts is ... in most cases
If you put em in without some locking method .........
It is almost a certain bet ... They will back out
btw ... I've used simple lock washers for decades with success

and
If you run Aluminum Heads ..........
I'd not do thread locker liquid as the material is easily damaged
Grady