Valve seals are leaking

[silverram323]

Was doing routine maintenance on the old 12v'er valve lash ect.......thought to do a boost leak test. At 18psi none 20psi valve seal start to hiss is this normal or time for some head work?

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[golfersmith]

Valve seals are not for holding pressure. This, I would say, is normal with rockers in place. Remove the rockers so all valves are closed and try again.
I've been wrong lots of times though.