Most cam makers recommend at least .080 on the intakes and .100 or more on the exhaust. Some recommend .120 on both, I have ran them( not intentionally) as close as .035 on the intakes and .060 on the exhaust, this was after having the heads cut down 6.5 CC on my old NHRA stocker and not checking V to P before starting. I ran that car for two more years after doing that before finding out the new V to P clearnances
I set my motors up with .080 on both now and I have never had a problem with those clearances, bracket, street or all out N/A Hi Po motors
as far as valve spring pressures I like 150 to 180 lbs on the seats and 325 to 375 lbs opened on a bracket motor, I have one motor , SB stroker with good valve train parts that I started and broke in the motor on a dyno with weaker springs during cam break in that has 175lbs on the seats and 425 lbs opened
He wanted the motor to live on the street and use NOS anytime he wanted
That was a long time ago and it is still living
