With the Draw-Thru (
sp) setup, high vacuum at the carb will keep PV
closed at all throttle positions. Carb'd draw-thru turbo's typically have a way to get the Power Valve Circuit to
OPEN when the Intake manifold transitions to positive boost pressure .
GM-BOP V6's and V8' turbo's used a specifically built Quadrajet that simply ran the PV vacuum circuit externally and used a proprietary vacuum switch mounted on the intake manifold to 'switch' the carbs PV circuit to open under boost.
I used a generic vacuum-dependent fuel line shutoff to 'switch' the Qjet's PV circuit on my Draw-Thru BOP setup.
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The 2300 bbl mentioned has the vacuum port for PV between the bores on bottom of carb base. All modern 2300's have a small ball popper valve there to prevent backfire blow-out of the PV. The vacuum chamber behind the PV can be sealed from the port and an external port drilled,tapped and added to circuit 'switched' by manifold boost pressure.
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A new option for
Blow-thru forced induction is a proprietary Power Valve (Holley type) made to
Open under Boost which basically operates backward from a normal PV. It stays closed until bost and is adjustable. This requires sealing the PV vacuum port and letting fuel bowl pressure (Boost) operate the PV. Seems like a good idea, I'm building a 2300 for the new PV option.
have fun