The rocker studs hold the guide plates down------always use some kind of lube/sealer if water jacket involved but most studs go into a boss cast on the head-some intake rocker studs will penetrate into intake port and can cause vacume leak. there are some longer studs to allow more thread surface(well actually, I think it started by placing the exhaust rocker higher up for correct geometry and they broke the bosses off so somebody did some longer studs-always use 7/16 thread, never use the 3/8 into alum. save the helicoil for repair option later. seal the threads into the intake ports or you will get a leaky, smoky,vacume leak.

Proper alignment of the process is vital