@hce
There is no exact boost number that lifts heads its cylinder pressure.
The harder you push(more boost) the more you build cylinder pressure.
Fueling, rpm, back pressure, heat all play into cylinder pressure
As a general rule 10-15psi is "safe"
I have a buddy running 20psi regularly and has seen 24psi on head studs that were torqued to yeild(he did all the calculations on them and found his most clamping force)
Anyway his is still running great
I have heard of some people making 25+ psi on 6.9 studs and others lifting at 15 psi.
I can tell you a 110cc pump will lift heads. I can think of 3 studded 6.9s that have lifted above 20psi.
It's all a educated guess
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