From the bottom of the top collar to top of installed seal you need 5/8” min.
Set up coil bind with .100 to .150 over cam lift, when checking the coil bind at lift check to see if1/3 or less of coils are touching if ½ of coils are touching each other you will get a ticking sound like lifter noises. It's call “coil bounce ”.
Some heads the inner springs will coil bind before outer spring coil binds, the ev and duel cam heads if you remove lower collar and just use spring shim. You increase coil bind and stop noisy top end, you still have to test coil bind limits and inspect coils at cam lift specification.
Check head oil drain hole for size at top of hole, many need to be open up or taper for proper oil drain flow.
Try to set up heads with 90-100 psi + value seat pressure.
Check value guide to stem clearance, normal ev get tighter
Cast iron guides need min of .001 clearances, bronze guides need .002 min clearances.
Bronze guide if worn you can knurl i.d. and size, don’t always have to be changed.
When you inspect value stem end if it flared coil bind can be to tight, or to many high rpm, check to make sure oiling system is working at highest pressure. Check rocker arm stem oiling hole for size and it’s open. Check rocker arm side clearance.
Shove & Sportster and early Ev rocker boxes need to be vent for cooling-air pressure relief-proper oil pressure.
Lube stem before installing into guide and seal before installing spring.