what makes a PV work

[GOTFEAR]

Well tha heck with FTZ i just cant waist all summer on my motor to be repaird so i just got a ESR mx 330 PV this is my first PV so what makes the valve open im thinking exhaust pressure? and is this adjustable im thinking spring pressure. they say just bolt on but im a fine tune freak.

[redrooster310r]

just got my esr 350 pv .....sweeet ...the valve works on exhasut pressure...dont know if the springs are adjustable....or even if you want to change them...

[C-LEIGH RACING]

On the ESR top end PVs, theres a small hole drilled up through the valve blade itself that feeds the presure to open the valve up.
All other types of PVs used on the Pro-x cylinders have a hole drilled up through the cylinder block on the back side of the valve up in the exhaust port roof.
Neil