noob valve spring question

I didn’t read through it again to see if this was discussed.......
Have you done a compression test?
Does it seem higher than you’d expect?

I know of three builds that all had the “it won’t rev over 4000” type of symptom....... where it ended up being the cam was installed wrong.
All three had the cam installed with the bottom keyway straight up, and the upper gear dot straight down.
That arrangement will have the cam advanced 2 1/2 teeth..... which is about 35*....... and the motor will run into a wall from 4000-4500.
In all three of these cases the car drove around fine until you tried to get it to rev..... and one of them had been being run like that for a couple of years.